diff --git a/CHANGELOG.md b/CHANGELOG.md
index 570b13482b..5a6091c73d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,23 @@
+# v1.7.21
+## 09/14/2021
+
+1. [](#new)
+    * Added `|yaml` filter to convert input to YAML
+    * Added `route` and `request` to `onPageNotFound` event
+    * Added file upload/remove support for `Flex Forms`
+    * Added support for `flex-required@: not exists` and `flex-required@: '!exists'` in blueprints
+    * Added `$object->getOriginalData()` to get flex objects data before it was modified with `update()`
+    * Throwing exceptions from Twig templates fires `onDisplayErrorPage.[code]` event allowing better error pages
+2. [](#improved)
+    * Use a simplified text-based `cron` field for scheduler
+    * Add timestamp to logging output of scheduler jobs to see when they ran
+3. [](#bugfix)
+    * Fixed escaping in PageIndex::getLevelListing()
+    * Fixed validation of `number` type [#3433](https://github.com/getgrav/grav/issues/3433)
+    * Fixed excessive `security.yaml` file creation [#3432](https://github.com/getgrav/grav/issues/3432)
+    * Fixed incorrect port :0 with nginx unix socket setup [#3439](https://github.com/getgrav/grav/issues/3439)
+    * Fixed `Session::setFlashCookieObject()` to use the same options as the main session cookie
+
 # v1.7.20
 ## 09/01/2021
 
diff --git a/composer.lock b/composer.lock
index f06c4a6010..8d2907f419 100644
--- a/composer.lock
+++ b/composer.lock
@@ -311,26 +311,26 @@
         },
         {
             "name": "doctrine/collections",
-            "version": "1.6.7",
+            "version": "1.6.8",
             "source": {
                 "type": "git",
                 "url": "https://github.com/doctrine/collections.git",
-                "reference": "55f8b799269a1a472457bd1a41b4f379d4cfba4a"
+                "reference": "1958a744696c6bb3bb0d28db2611dc11610e78af"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/doctrine/collections/zipball/55f8b799269a1a472457bd1a41b4f379d4cfba4a",
-                "reference": "55f8b799269a1a472457bd1a41b4f379d4cfba4a",
+                "url": "https://api.github.com/repos/doctrine/collections/zipball/1958a744696c6bb3bb0d28db2611dc11610e78af",
+                "reference": "1958a744696c6bb3bb0d28db2611dc11610e78af",
                 "shasum": ""
             },
             "require": {
                 "php": "^7.1.3 || ^8.0"
             },
             "require-dev": {
-                "doctrine/coding-standard": "^6.0",
-                "phpstan/phpstan-shim": "^0.9.2",
-                "phpunit/phpunit": "^7.0",
-                "vimeo/psalm": "^3.8.1"
+                "doctrine/coding-standard": "^9.0",
+                "phpstan/phpstan": "^0.12",
+                "phpunit/phpunit": "^7.5 || ^8.5 || ^9.1.5",
+                "vimeo/psalm": "^4.2.1"
             },
             "type": "library",
             "autoload": {
@@ -374,9 +374,9 @@
             ],
             "support": {
                 "issues": "https://github.com/doctrine/collections/issues",
-                "source": "https://github.com/doctrine/collections/tree/1.6.7"
+                "source": "https://github.com/doctrine/collections/tree/1.6.8"
             },
-            "time": "2020-07-27T17:53:49+00:00"
+            "time": "2021-08-10T18:51:53+00:00"
         },
         {
             "name": "donatj/phpuseragentparser",
@@ -642,16 +642,16 @@
         },
         {
             "name": "filp/whoops",
-            "version": "2.14.0",
+            "version": "2.14.1",
             "source": {
                 "type": "git",
                 "url": "https://github.com/filp/whoops.git",
-                "reference": "fdf92f03e150ed84d5967a833ae93abffac0315b"
+                "reference": "15ead64e9828f0fc90932114429c4f7923570cb1"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/filp/whoops/zipball/fdf92f03e150ed84d5967a833ae93abffac0315b",
-                "reference": "fdf92f03e150ed84d5967a833ae93abffac0315b",
+                "url": "https://api.github.com/repos/filp/whoops/zipball/15ead64e9828f0fc90932114429c4f7923570cb1",
+                "reference": "15ead64e9828f0fc90932114429c4f7923570cb1",
                 "shasum": ""
             },
             "require": {
@@ -701,7 +701,7 @@
             ],
             "support": {
                 "issues": "https://github.com/filp/whoops/issues",
-                "source": "https://github.com/filp/whoops/tree/2.14.0"
+                "source": "https://github.com/filp/whoops/tree/2.14.1"
             },
             "funding": [
                 {
@@ -709,7 +709,7 @@
                     "type": "github"
                 }
             ],
-            "time": "2021-07-13T12:00:00+00:00"
+            "time": "2021-08-29T12:00:00+00:00"
         },
         {
             "name": "getgrav/cache",
@@ -2258,16 +2258,16 @@
         },
         {
             "name": "symfony/console",
-            "version": "v4.4.29",
+            "version": "v4.4.30",
             "source": {
                 "type": "git",
                 "url": "https://github.com/symfony/console.git",
-                "reference": "8baf0bbcfddfde7d7225ae8e04705cfd1081cd7b"
+                "reference": "a3f7189a0665ee33b50e9e228c46f50f5acbed22"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/symfony/console/zipball/8baf0bbcfddfde7d7225ae8e04705cfd1081cd7b",
-                "reference": "8baf0bbcfddfde7d7225ae8e04705cfd1081cd7b",
+                "url": "https://api.github.com/repos/symfony/console/zipball/a3f7189a0665ee33b50e9e228c46f50f5acbed22",
+                "reference": "a3f7189a0665ee33b50e9e228c46f50f5acbed22",
                 "shasum": ""
             },
             "require": {
@@ -2328,7 +2328,7 @@
             "description": "Eases the creation of beautiful and testable command line interfaces",
             "homepage": "https://symfony.com",
             "support": {
-                "source": "https://github.com/symfony/console/tree/v4.4.29"
+                "source": "https://github.com/symfony/console/tree/v4.4.30"
             },
             "funding": [
                 {
@@ -2344,7 +2344,7 @@
                     "type": "tidelift"
                 }
             ],
-            "time": "2021-07-27T19:04:53+00:00"
+            "time": "2021-08-25T19:27:26+00:00"
         },
         {
             "name": "symfony/contracts",
@@ -2442,16 +2442,16 @@
         },
         {
             "name": "symfony/event-dispatcher",
-            "version": "v4.4.27",
+            "version": "v4.4.30",
             "source": {
                 "type": "git",
                 "url": "https://github.com/symfony/event-dispatcher.git",
-                "reference": "958a128b184fcf0ba45ec90c0e88554c9327c2e9"
+                "reference": "2fe81680070043c4c80e7cedceb797e34f377bac"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/symfony/event-dispatcher/zipball/958a128b184fcf0ba45ec90c0e88554c9327c2e9",
-                "reference": "958a128b184fcf0ba45ec90c0e88554c9327c2e9",
+                "url": "https://api.github.com/repos/symfony/event-dispatcher/zipball/2fe81680070043c4c80e7cedceb797e34f377bac",
+                "reference": "2fe81680070043c4c80e7cedceb797e34f377bac",
                 "shasum": ""
             },
             "require": {
@@ -2506,7 +2506,7 @@
             "description": "Provides tools that allow your application components to communicate with each other by dispatching events and listening to them",
             "homepage": "https://symfony.com",
             "support": {
-                "source": "https://github.com/symfony/event-dispatcher/tree/v4.4.27"
+                "source": "https://github.com/symfony/event-dispatcher/tree/v4.4.30"
             },
             "funding": [
                 {
@@ -2522,7 +2522,7 @@
                     "type": "tidelift"
                 }
             ],
-            "time": "2021-07-23T15:41:52+00:00"
+            "time": "2021-08-04T20:31:23+00:00"
         },
         {
             "name": "symfony/http-client",
@@ -3009,16 +3009,16 @@
         },
         {
             "name": "symfony/process",
-            "version": "v4.4.27",
+            "version": "v4.4.30",
             "source": {
                 "type": "git",
                 "url": "https://github.com/symfony/process.git",
-                "reference": "0b7dc5599ac4aa6d7b936c8f7d10abae64f6cf7f"
+                "reference": "13d3161ef63a8ec21eeccaaf9a4d7f784a87a97d"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/symfony/process/zipball/0b7dc5599ac4aa6d7b936c8f7d10abae64f6cf7f",
-                "reference": "0b7dc5599ac4aa6d7b936c8f7d10abae64f6cf7f",
+                "url": "https://api.github.com/repos/symfony/process/zipball/13d3161ef63a8ec21eeccaaf9a4d7f784a87a97d",
+                "reference": "13d3161ef63a8ec21eeccaaf9a4d7f784a87a97d",
                 "shasum": ""
             },
             "require": {
@@ -3051,7 +3051,7 @@
             "description": "Executes commands in sub-processes",
             "homepage": "https://symfony.com",
             "support": {
-                "source": "https://github.com/symfony/process/tree/v4.4.27"
+                "source": "https://github.com/symfony/process/tree/v4.4.30"
             },
             "funding": [
                 {
@@ -3067,20 +3067,20 @@
                     "type": "tidelift"
                 }
             ],
-            "time": "2021-07-23T15:41:52+00:00"
+            "time": "2021-08-04T20:31:23+00:00"
         },
         {
             "name": "symfony/var-dumper",
-            "version": "v4.4.27",
+            "version": "v4.4.30",
             "source": {
                 "type": "git",
                 "url": "https://github.com/symfony/var-dumper.git",
-                "reference": "391d6d0e7a06ab54eb7c38fab29b8d174471b3ba"
+                "reference": "7f65c44c2ce80d3a0fcdb6385ee0ad535e45660c"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/symfony/var-dumper/zipball/391d6d0e7a06ab54eb7c38fab29b8d174471b3ba",
-                "reference": "391d6d0e7a06ab54eb7c38fab29b8d174471b3ba",
+                "url": "https://api.github.com/repos/symfony/var-dumper/zipball/7f65c44c2ce80d3a0fcdb6385ee0ad535e45660c",
+                "reference": "7f65c44c2ce80d3a0fcdb6385ee0ad535e45660c",
                 "shasum": ""
             },
             "require": {
@@ -3140,7 +3140,7 @@
                 "dump"
             ],
             "support": {
-                "source": "https://github.com/symfony/var-dumper/tree/v4.4.27"
+                "source": "https://github.com/symfony/var-dumper/tree/v4.4.30"
             },
             "funding": [
                 {
@@ -3156,7 +3156,7 @@
                     "type": "tidelift"
                 }
             ],
-            "time": "2021-07-23T15:41:52+00:00"
+            "time": "2021-08-04T20:31:23+00:00"
         },
         {
             "name": "symfony/yaml",
@@ -3580,20 +3580,20 @@
         },
         {
             "name": "codeception/lib-innerbrowser",
-            "version": "1.5.0",
+            "version": "1.5.1",
             "source": {
                 "type": "git",
                 "url": "https://github.com/Codeception/lib-innerbrowser.git",
-                "reference": "4b0d89b37fe454e060a610a85280a87ab4f534f1"
+                "reference": "31b4b56ad53c3464fcb2c0a14d55a51a201bd3c2"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/Codeception/lib-innerbrowser/zipball/4b0d89b37fe454e060a610a85280a87ab4f534f1",
-                "reference": "4b0d89b37fe454e060a610a85280a87ab4f534f1",
+                "url": "https://api.github.com/repos/Codeception/lib-innerbrowser/zipball/31b4b56ad53c3464fcb2c0a14d55a51a201bd3c2",
+                "reference": "31b4b56ad53c3464fcb2c0a14d55a51a201bd3c2",
                 "shasum": ""
             },
             "require": {
-                "codeception/codeception": "*@dev",
+                "codeception/codeception": "4.*@dev",
                 "ext-dom": "*",
                 "ext-json": "*",
                 "ext-mbstring": "*",
@@ -3634,9 +3634,9 @@
             ],
             "support": {
                 "issues": "https://github.com/Codeception/lib-innerbrowser/issues",
-                "source": "https://github.com/Codeception/lib-innerbrowser/tree/1.5.0"
+                "source": "https://github.com/Codeception/lib-innerbrowser/tree/1.5.1"
             },
-            "time": "2021-04-23T06:18:29+00:00"
+            "time": "2021-08-30T15:21:42+00:00"
         },
         {
             "name": "codeception/module-asserts",
@@ -4569,16 +4569,16 @@
         },
         {
             "name": "phpstan/phpstan",
-            "version": "0.12.94",
+            "version": "0.12.98",
             "source": {
                 "type": "git",
                 "url": "https://github.com/phpstan/phpstan.git",
-                "reference": "3d0ba4c198a24e3c3fc489f3ec6ac9612c4be5d6"
+                "reference": "3bb7cc246c057405dd5e290c3ecc62ab51d57e00"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/phpstan/phpstan/zipball/3d0ba4c198a24e3c3fc489f3ec6ac9612c4be5d6",
-                "reference": "3d0ba4c198a24e3c3fc489f3ec6ac9612c4be5d6",
+                "url": "https://api.github.com/repos/phpstan/phpstan/zipball/3bb7cc246c057405dd5e290c3ecc62ab51d57e00",
+                "reference": "3bb7cc246c057405dd5e290c3ecc62ab51d57e00",
                 "shasum": ""
             },
             "require": {
@@ -4609,7 +4609,7 @@
             "description": "PHPStan - PHP Static Analysis Tool",
             "support": {
                 "issues": "https://github.com/phpstan/phpstan/issues",
-                "source": "https://github.com/phpstan/phpstan/tree/0.12.94"
+                "source": "https://github.com/phpstan/phpstan/tree/0.12.98"
             },
             "funding": [
                 {
@@ -4629,7 +4629,7 @@
                     "type": "tidelift"
                 }
             ],
-            "time": "2021-07-30T09:05:27+00:00"
+            "time": "2021-09-02T12:33:01+00:00"
         },
         {
             "name": "phpstan/phpstan-deprecation-rules",
@@ -5002,16 +5002,16 @@
         },
         {
             "name": "phpunit/phpunit",
-            "version": "9.5.8",
+            "version": "9.5.9",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/phpunit.git",
-                "reference": "191768ccd5c85513b4068bdbe99bb6390c7d54fb"
+                "reference": "ea8c2dfb1065eb35a79b3681eee6e6fb0a6f273b"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/sebastianbergmann/phpunit/zipball/191768ccd5c85513b4068bdbe99bb6390c7d54fb",
-                "reference": "191768ccd5c85513b4068bdbe99bb6390c7d54fb",
+                "url": "https://api.github.com/repos/sebastianbergmann/phpunit/zipball/ea8c2dfb1065eb35a79b3681eee6e6fb0a6f273b",
+                "reference": "ea8c2dfb1065eb35a79b3681eee6e6fb0a6f273b",
                 "shasum": ""
             },
             "require": {
@@ -5089,7 +5089,7 @@
             ],
             "support": {
                 "issues": "https://github.com/sebastianbergmann/phpunit/issues",
-                "source": "https://github.com/sebastianbergmann/phpunit/tree/9.5.8"
+                "source": "https://github.com/sebastianbergmann/phpunit/tree/9.5.9"
             },
             "funding": [
                 {
@@ -5101,7 +5101,7 @@
                     "type": "github"
                 }
             ],
-            "time": "2021-07-31T15:17:34+00:00"
+            "time": "2021-08-31T06:47:40+00:00"
         },
         {
             "name": "psr/http-client",
@@ -6008,6 +6008,7 @@
                     "type": "github"
                 }
             ],
+            "abandoned": true,
             "time": "2020-09-28T06:45:17+00:00"
         },
         {
@@ -6326,16 +6327,16 @@
         },
         {
             "name": "symfony/dom-crawler",
-            "version": "v5.3.4",
+            "version": "v5.3.7",
             "source": {
                 "type": "git",
                 "url": "https://github.com/symfony/dom-crawler.git",
-                "reference": "2dd8890bd01be59a5221999c05ccf0fcafcb354f"
+                "reference": "c7eef3a60ccfdd8eafe07f81652e769ac9c7146c"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/symfony/dom-crawler/zipball/2dd8890bd01be59a5221999c05ccf0fcafcb354f",
-                "reference": "2dd8890bd01be59a5221999c05ccf0fcafcb354f",
+                "url": "https://api.github.com/repos/symfony/dom-crawler/zipball/c7eef3a60ccfdd8eafe07f81652e769ac9c7146c",
+                "reference": "c7eef3a60ccfdd8eafe07f81652e769ac9c7146c",
                 "shasum": ""
             },
             "require": {
@@ -6381,7 +6382,7 @@
             "description": "Eases DOM navigation for HTML and XML documents",
             "homepage": "https://symfony.com",
             "support": {
-                "source": "https://github.com/symfony/dom-crawler/tree/v5.3.4"
+                "source": "https://github.com/symfony/dom-crawler/tree/v5.3.7"
             },
             "funding": [
                 {
@@ -6397,20 +6398,20 @@
                     "type": "tidelift"
                 }
             ],
-            "time": "2021-07-23T15:55:36+00:00"
+            "time": "2021-08-29T19:32:13+00:00"
         },
         {
             "name": "symfony/finder",
-            "version": "v5.3.4",
+            "version": "v5.3.7",
             "source": {
                 "type": "git",
                 "url": "https://github.com/symfony/finder.git",
-                "reference": "17f50e06018baec41551a71a15731287dbaab186"
+                "reference": "a10000ada1e600d109a6c7632e9ac42e8bf2fb93"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/symfony/finder/zipball/17f50e06018baec41551a71a15731287dbaab186",
-                "reference": "17f50e06018baec41551a71a15731287dbaab186",
+                "url": "https://api.github.com/repos/symfony/finder/zipball/a10000ada1e600d109a6c7632e9ac42e8bf2fb93",
+                "reference": "a10000ada1e600d109a6c7632e9ac42e8bf2fb93",
                 "shasum": ""
             },
             "require": {
@@ -6443,7 +6444,7 @@
             "description": "Finds files and directories via an intuitive fluent interface",
             "homepage": "https://symfony.com",
             "support": {
-                "source": "https://github.com/symfony/finder/tree/v5.3.4"
+                "source": "https://github.com/symfony/finder/tree/v5.3.7"
             },
             "funding": [
                 {
@@ -6459,7 +6460,7 @@
                     "type": "tidelift"
                 }
             ],
-            "time": "2021-07-23T15:54:19+00:00"
+            "time": "2021-08-04T21:20:46+00:00"
         },
         {
             "name": "theseer/tokenizer",
diff --git a/system/blueprints/config/scheduler.yaml b/system/blueprints/config/scheduler.yaml
index caa7711678..a8dce314bd 100644
--- a/system/blueprints/config/scheduler.yaml
+++ b/system/blueprints/config/scheduler.yaml
@@ -47,7 +47,8 @@ form:
               label: PLUGIN_ADMIN.EXTRA_ARGUMENTS
               placeholder: '-lah'
             .at:
-              type: cron
+              type: text
+              wrapper_classes: cron-selector
               label: PLUGIN_ADMIN.SCHEDULER_RUNAT
               help: PLUGIN_ADMIN.SCHEDULER_RUNAT_HELP
               placeholder: '* * * * *'
diff --git a/system/defines.php b/system/defines.php
index 9844b6b885..9ab384faba 100644
--- a/system/defines.php
+++ b/system/defines.php
@@ -9,7 +9,7 @@
 
 // Some standard defines
 define('GRAV', true);
-define('GRAV_VERSION', '1.7.20');
+define('GRAV_VERSION', '1.7.21');
 define('GRAV_SCHEMA', '1.7.0_2020-11-20_1');
 define('GRAV_TESTING', false);
 
diff --git a/system/src/Grav/Common/Config/Setup.php b/system/src/Grav/Common/Config/Setup.php
index 83a2763951..6ff7372d0b 100644
--- a/system/src/Grav/Common/Config/Setup.php
+++ b/system/src/Grav/Common/Config/Setup.php
@@ -400,8 +400,12 @@ protected function check(UniformResourceLocator $locator)
                 $this->initializeLocator($locator);
             }
 
-            // Create security.yaml if it doesn't exist.
-            $filename = $locator->findResource(static::$securityFile, true, true);
+            // Create security.yaml salt if it doesn't exist into existing configuration environment if possible.
+            $securityFile = basename(static::$securityFile);
+            $securityFolder = substr(static::$securityFile, 0, -\strlen($securityFile));
+            $securityFolder = $locator->findResource($securityFolder, true) ?: $locator->findResource($securityFolder, true, true);
+            $filename = "{$securityFolder}/{$securityFile}";
+
             $security_file = CompiledYamlFile::instance($filename);
             $security_content = (array)$security_file->content();
 
diff --git a/system/src/Grav/Common/Data/Validation.php b/system/src/Grav/Common/Data/Validation.php
index f69c841fc0..7ee60e4155 100644
--- a/system/src/Grav/Common/Data/Validation.php
+++ b/system/src/Grav/Common/Data/Validation.php
@@ -538,8 +538,10 @@ public static function typeNumber($value, array $params, array $field)
 
         if (isset($params['step'])) {
             $step = (float)$params['step'];
+            // Count of how many steps we are above/below the minimum value.
+            $pos = ($value - $min) / $step;
 
-            return fmod($value - $min, $step) === 0.0;
+            return is_int(static::filterNumber($pos, $params, $field));
         }
 
         return true;
diff --git a/system/src/Grav/Common/Flex/Types/Pages/PageIndex.php b/system/src/Grav/Common/Flex/Types/Pages/PageIndex.php
index e2938aeb48..dd06f58688 100644
--- a/system/src/Grav/Common/Flex/Types/Pages/PageIndex.php
+++ b/system/src/Grav/Common/Flex/Types/Pages/PageIndex.php
@@ -674,12 +674,12 @@ protected function getLevelListingRecurse(array $options): array
                     $count = $filters ? $tmp->filterBy($filters, true)->count() : null;
                     $route = $child->getRoute();
                     $payload = [
-                        'item-key' => basename($child->rawRoute() ?? $child->getKey()),
+                        'item-key' => htmlspecialchars(basename($child->rawRoute() ?? $child->getKey())),
                         'icon' => $icon,
                         'title' => htmlspecialchars($child->menu()),
                         'route' => [
-                            'display' => ($route ? ($route->toString(false) ?: '/') : null) ?? '',
-                            'raw' => $child->rawRoute(),
+                            'display' => htmlspecialchars(($route ? ($route->toString(false) ?: '/') : null) ?? ''),
+                            'raw' => htmlspecialchars($child->rawRoute()),
                         ],
                         'modified' => $this->jsDate($child->modified()),
                         'child_count' => $child_count ?: null,
diff --git a/system/src/Grav/Common/Flex/Types/UserGroups/UserGroupObject.php b/system/src/Grav/Common/Flex/Types/UserGroups/UserGroupObject.php
index fb69eab68f..ea68fa1bf8 100644
--- a/system/src/Grav/Common/Flex/Types/UserGroups/UserGroupObject.php
+++ b/system/src/Grav/Common/Flex/Types/UserGroups/UserGroupObject.php
@@ -41,6 +41,14 @@ public static function getCachedMethods(): array
         ] + parent::getCachedMethods();
     }
 
+    /**
+     * @return string
+     */
+    public function getTitle(): string
+    {
+        return $this->getProperty('readableName');
+    }
+
     /**
      * Checks user authorization to the action.
      *
diff --git a/system/src/Grav/Common/Flex/Types/Users/UserObject.php b/system/src/Grav/Common/Flex/Types/Users/UserObject.php
index 82b9f7c4f1..310c313fe6 100644
--- a/system/src/Grav/Common/Flex/Types/Users/UserObject.php
+++ b/system/src/Grav/Common/Flex/Types/Users/UserObject.php
@@ -32,6 +32,7 @@
 use Grav\Common\User\Traits\UserTrait;
 use Grav\Framework\File\Formatter\JsonFormatter;
 use Grav\Framework\File\Formatter\YamlFormatter;
+use Grav\Framework\Filesystem\Filesystem;
 use Grav\Framework\Flex\Flex;
 use Grav\Framework\Flex\FlexDirectory;
 use Grav\Framework\Flex\Storage\FileStorage;
@@ -305,6 +306,14 @@ public function getProperty($property, $default = null)
         return $value;
     }
 
+    /**
+     * @return UserGroupIndex
+     */
+    public function getRoles(): UserGroupIndex
+    {
+        return $this->getGroups();
+    }
+
     /**
      * Convert object into an array.
      *
@@ -702,6 +711,7 @@ protected function getOriginalMedia()
 
     /**
      * @param array $files
+     * @return void
      */
     protected function setUpdatedMedia(array $files): void
     {
@@ -713,9 +723,12 @@ protected function setUpdatedMedia(array $files): void
             return;
         }
 
+        $filesystem = Filesystem::getInstance(false);
+
         $list = [];
         $list_original = [];
         foreach ($files as $field => $group) {
+            // Ignore files without a field.
             if ($field === '') {
                 continue;
             }
@@ -737,7 +750,7 @@ protected function setUpdatedMedia(array $files): void
                 }
 
                 if ($file) {
-                    // Check file upload against media limits.
+                    // Check file upload against media limits (except for max size).
                     $filename = $media->checkUploadedFile($file, $filename, ['filesize' => 0] + $settings);
                 }
 
@@ -761,15 +774,19 @@ protected function setUpdatedMedia(array $files): void
                     continue;
                 }
 
+                // Calculate path without the retina scaling factor.
+                $realpath = $filesystem->pathname($filepath) . str_replace(['@3x', '@2x'], '', basename($filepath));
+
                 $list[$filename] = [$file, $settings];
 
+                $path = str_replace('.', "\n", $field);
                 if (null !== $data) {
                     $data['name'] = $filename;
                     $data['path'] = $filepath;
 
-                    $this->setNestedProperty("{$field}\n{$filepath}", $data, "\n");
+                    $this->setNestedProperty("{$path}\n{$realpath}", $data, "\n");
                 } else {
-                    $this->unsetNestedProperty("{$field}\n{$filepath}", "\n");
+                    $this->unsetNestedProperty("{$path}\n{$realpath}", "\n");
                 }
             }
         }
diff --git a/system/src/Grav/Common/Grav.php b/system/src/Grav/Common/Grav.php
index c9097eea8a..ffbb508183 100644
--- a/system/src/Grav/Common/Grav.php
+++ b/system/src/Grav/Common/Grav.php
@@ -9,6 +9,7 @@
 
 namespace Grav\Common;
 
+use Composer\Autoload\ClassLoader;
 use Grav\Common\Config\Config;
 use Grav\Common\Config\Setup;
 use Grav\Common\Helpers\Exif;
@@ -152,6 +153,13 @@ public static function instance(array $values = [])
     {
         if (null === self::$instance) {
             self::$instance = static::load($values);
+
+            /** @var ClassLoader|null $loader */
+            $loader = self::$instance['loader'] ?? null;
+            if ($loader) {
+                // Load fix for Deferred Twig Extension
+                $loader->addPsr4('Phive\\Twig\\Extensions\\Deferred\\', LIB_DIR . 'Phive/Twig/Extensions/Deferred/', true);
+            }
         } elseif ($values) {
             $instance = self::$instance;
             foreach ($values as $key => $value) {
diff --git a/system/src/Grav/Common/Processors/PagesProcessor.php b/system/src/Grav/Common/Processors/PagesProcessor.php
index d5d1d46678..470ca907b5 100644
--- a/system/src/Grav/Common/Processors/PagesProcessor.php
+++ b/system/src/Grav/Common/Processors/PagesProcessor.php
@@ -10,6 +10,7 @@
 namespace Grav\Common\Processors;
 
 use Grav\Common\Page\Interfaces\PageInterface;
+use Grav\Framework\RequestHandler\Exception\RequestException;
 use Grav\Plugin\Form\Forms;
 use RocketTheme\Toolbox\Event\Event;
 use Psr\Http\Message\ResponseInterface;
@@ -48,8 +49,17 @@ public function process(ServerRequestInterface $request, RequestHandlerInterface
         $page = $this->container['page'];
 
         if (!$page->routable()) {
+            $exception = new RequestException($request, 'Page Not Found', 404);
+            $route = $this->container['route'];
             // If no page found, fire event
-            $event = new Event(['page' => $page]);
+            $event = new Event([
+                'page' => $page,
+                'code' => $exception->getCode(),
+                'message' => $exception->getMessage(),
+                'exception' => $exception,
+                'route' => $route,
+                'request' => $request
+            ]);
             $event->page = null;
             $event = $this->container->fireEvent('onPageNotFound', $event);
 
diff --git a/system/src/Grav/Common/Scheduler/Job.php b/system/src/Grav/Common/Scheduler/Job.php
index f21c26defd..94fbaf102c 100644
--- a/system/src/Grav/Common/Scheduler/Job.php
+++ b/system/src/Grav/Common/Scheduler/Job.php
@@ -390,7 +390,9 @@ private function postRun()
         if (count($this->outputTo) > 0) {
             foreach ($this->outputTo as $file) {
                 $output_mode = $this->outputMode === 'append' ? FILE_APPEND | LOCK_EX : LOCK_EX;
-                file_put_contents($file, $this->output, $output_mode);
+                $timestamp = (new DateTime('now'))->format('c');
+                $output = $timestamp . "\n" . str_pad('', strlen($timestamp), '>') . "\n" . $this->output;
+                file_put_contents($file, $output, $output_mode);
             }
         }
 
diff --git a/system/src/Grav/Common/Session.php b/system/src/Grav/Common/Session.php
index 8856e7a0a4..2dbc3073ad 100644
--- a/system/src/Grav/Common/Session.php
+++ b/system/src/Grav/Common/Session.php
@@ -12,6 +12,7 @@
 use Grav\Common\Form\FormFlash;
 use Grav\Events\SessionStartEvent;
 use Grav\Plugin\Form\Forms;
+use JsonException;
 use function is_string;
 
 /**
@@ -148,10 +149,11 @@ public function getFlashObject($name)
      * @param mixed $object
      * @param int $time
      * @return $this
+     * @throws JsonException
      */
     public function setFlashCookieObject($name, $object, $time = 60)
     {
-        setcookie($name, json_encode($object), time() + $time, '/');
+        setcookie($name, json_encode($object, JSON_THROW_ON_ERROR), $this->getCookieOptions($time));
 
         return $this;
     }
@@ -161,13 +163,15 @@ public function setFlashCookieObject($name, $object, $time = 60)
      *
      * @param string $name
      * @return mixed|null
+     * @throws JsonException
      */
     public function getFlashCookieObject($name)
     {
         if (isset($_COOKIE[$name])) {
-            $object = json_decode($_COOKIE[$name], false);
-            setcookie($name, '', time() - 3600, '/');
-            return $object;
+            $cookie = $_COOKIE[$name];
+            setcookie($name, '', $this->getCookieOptions(-42000));
+
+            return json_decode($cookie, false, 512, JSON_THROW_ON_ERROR);
         }
 
         return null;
diff --git a/system/src/Grav/Common/Twig/Exception/TwigException.php b/system/src/Grav/Common/Twig/Exception/TwigException.php
new file mode 100644
index 0000000000..8f543dcc1e
--- /dev/null
+++ b/system/src/Grav/Common/Twig/Exception/TwigException.php
@@ -0,0 +1,19 @@
+<?php
+
+/**
+ * @package    Grav\Common\Twig\Exception
+ *
+ * @copyright  Copyright (c) 2015 - 2021 Trilby Media, LLC. All rights reserved.
+ * @license    MIT License; see LICENSE file for details.
+ */
+
+namespace Grav\Common\Twig\Exception;
+
+/**
+ * TwigException gets thrown when you use {% throw code message %} in twig.
+ *
+ * This allows Grav to catch 401, 403 and 404 exceptions and display proper error page.
+ */
+class TwigException extends \RuntimeException
+{
+}
diff --git a/system/src/Grav/Common/Twig/Extension/GravExtension.php b/system/src/Grav/Common/Twig/Extension/GravExtension.php
index 2c6b854360..5b4a16002a 100644
--- a/system/src/Grav/Common/Twig/Extension/GravExtension.php
+++ b/system/src/Grav/Common/Twig/Extension/GravExtension.php
@@ -155,6 +155,7 @@ public function getFilters()
             new TwigFilter('bool', [$this, 'boolFilter']),
             new TwigFilter('float', [$this, 'floatFilter'], ['is_safe' => ['all']]),
             new TwigFilter('array', [$this, 'arrayFilter']),
+            new TwigFilter('yaml', [$this, 'yamlFilter']),
 
             // Object Types
             new TwigFilter('get_type', [$this, 'getTypeFunc']),
@@ -807,6 +808,17 @@ public function arrayFilter($input)
         return (array)$input;
     }
 
+    /**
+     * @param array|object $value
+     * @param int|null $inline
+     * @param int|null $indent
+     * @return string
+     */
+    public function yamlFilter($value, $inline = null, $indent = null): string
+    {
+        return Yaml::dump($value, $inline, $indent);
+    }
+
     /**
      * @param Environment $twig
      * @return string
diff --git a/system/src/Grav/Common/Twig/Node/TwigNodeThrow.php b/system/src/Grav/Common/Twig/Node/TwigNodeThrow.php
index 1a32a91a37..3bfe6124e1 100644
--- a/system/src/Grav/Common/Twig/Node/TwigNodeThrow.php
+++ b/system/src/Grav/Common/Twig/Node/TwigNodeThrow.php
@@ -43,7 +43,7 @@ public function compile(Compiler $compiler): void
         $compiler->addDebugInfo($this);
 
         $compiler
-            ->write('throw new \RuntimeException(')
+            ->write('throw new \Grav\Common\Twig\Exception\TwigException(')
             ->subcompile($this->getNode('message'))
             ->write(', ')
             ->write($this->getAttribute('code') ?: 500)
diff --git a/system/src/Grav/Common/Twig/Twig.php b/system/src/Grav/Common/Twig/Twig.php
index 2796c0d458..ef74ce75ab 100644
--- a/system/src/Grav/Common/Twig/Twig.php
+++ b/system/src/Grav/Common/Twig/Twig.php
@@ -16,6 +16,7 @@
 use Grav\Common\Language\LanguageCodes;
 use Grav\Common\Page\Interfaces\PageInterface;
 use Grav\Common\Page\Pages;
+use Grav\Common\Twig\Exception\TwigException;
 use Grav\Common\Twig\Extension\FilesystemExtension;
 use Grav\Common\Twig\Extension\GravExtension;
 use Grav\Common\Utils;
@@ -26,6 +27,7 @@
 use Twig\Cache\FilesystemCache;
 use Twig\Environment;
 use Twig\Error\LoaderError;
+use Twig\Error\RuntimeError;
 use Twig\Extension\CoreExtension;
 use Twig\Extension\DebugExtension;
 use Twig\Extension\StringLoaderExtension;
@@ -404,38 +406,63 @@ public function processString($string, array $vars = [])
      */
     public function processSite($format = null, array $vars = [])
     {
-        // set the page now its been processed
-        $this->grav->fireEvent('onTwigSiteVariables');
-        /** @var Pages $pages */
-        $pages = $this->grav['pages'];
-        /** @var PageInterface $page */
-        $page = $this->grav['page'];
-        $content = $page->content();
+        try {
+            $grav = $this->grav;
 
-        $twig_vars = $this->twig_vars;
+            // set the page now its been processed
+            $grav->fireEvent('onTwigSiteVariables');
 
-        $twig_vars['theme'] = $this->grav['config']->get('theme');
-        $twig_vars['pages'] = $pages->root();
-        $twig_vars['page'] = $page;
-        $twig_vars['header'] = $page->header();
-        $twig_vars['media'] = $page->media();
-        $twig_vars['content'] = $content;
-
-        // determine if params are set, if so disable twig cache
-        $params = $this->grav['uri']->params(null, true);
-        if (!empty($params)) {
-            $this->twig->setCache(false);
-        }
+            /** @var Pages $pages */
+            $pages = $grav['pages'];
+
+            /** @var PageInterface $page */
+            $page = $grav['page'];
+
+            $twig_vars = $this->twig_vars;
+            $twig_vars['theme'] = $grav['config']->get('theme');
+            $twig_vars['pages'] = $pages->root();
+            $twig_vars['page'] = $page;
+            $twig_vars['header'] = $page->header();
+            $twig_vars['media'] = $page->media();
+            $twig_vars['content'] = $page->content();
+
+            // determine if params are set, if so disable twig cache
+            $params = $grav['uri']->params(null, true);
+            if (!empty($params)) {
+                $this->twig->setCache(false);
+            }
 
-        // Get Twig template layout
-        $template = $this->getPageTwigTemplate($page, $format);
-        $page->templateFormat($format);
+            // Get Twig template layout
+            $template = $this->getPageTwigTemplate($page, $format);
+            $page->templateFormat($format);
 
-        try {
             $output = $this->twig->render($template, $vars + $twig_vars);
         } catch (LoaderError $e) {
-            $error_msg = $e->getMessage();
-            throw new RuntimeException($error_msg, 400, $e);
+            throw new RuntimeException($e->getMessage(), 400, $e);
+        } catch (RuntimeError $e) {
+            $prev = $e->getPrevious();
+            if ($prev instanceof TwigException) {
+                $code = $prev->getCode() ?: 500;
+                // Fire onPageNotFound event.
+                $event = new Event([
+                    'page' => $page,
+                    'code' => $code,
+                    'message' => $prev->getMessage(),
+                    'exception' => $prev,
+                    'route' => $grav['route'],
+                    'request' => $grav['request']
+                ]);
+                $event = $grav->fireEvent("onDisplayErrorPage.{$code}", $event);
+                $newPage = $event['page'];
+                if ($newPage && $newPage !== $page) {
+                    unset($grav['page']);
+                    $grav['page'] = $newPage;
+
+                    return $this->processSite($newPage->templateFormat(), $vars);
+                }
+            }
+
+            throw $e;
         }
 
         return $output;
diff --git a/system/src/Grav/Common/Uri.php b/system/src/Grav/Common/Uri.php
index c7f71048ed..de325bbe2c 100644
--- a/system/src/Grav/Common/Uri.php
+++ b/system/src/Grav/Common/Uri.php
@@ -1261,7 +1261,7 @@ protected function createFromEnvironment(array $env)
             $this->port = null;
         }
 
-        if ($this->hasStandardPort()) {
+        if ($this->port === 0 || $this->hasStandardPort()) {
             $this->port = null;
         }
 
@@ -1314,11 +1314,13 @@ protected function createFromString($url)
         if ($parts === false) {
             throw new RuntimeException('Malformed URL: ' . $url);
         }
+        $port = (int)($parts['port'] ?? 0);
+
         $this->scheme = $parts['scheme'] ?? null;
         $this->user = $parts['user'] ?? null;
         $this->password = $parts['pass'] ?? null;
         $this->host = $parts['host'] ?? null;
-        $this->port = isset($parts['port']) ? (int)$parts['port'] : null;
+        $this->port = $port ?: null;
         $this->path = $parts['path'] ?? '';
         $this->query = $parts['query'] ?? '';
         $this->fragment = $parts['fragment'] ?? null;
diff --git a/system/src/Grav/Framework/Flex/FlexDirectory.php b/system/src/Grav/Framework/Flex/FlexDirectory.php
index 43fe000810..29f1490f82 100644
--- a/system/src/Grav/Framework/Flex/FlexDirectory.php
+++ b/system/src/Grav/Framework/Flex/FlexDirectory.php
@@ -836,13 +836,22 @@ protected function dynamicFlexField(array &$field, $property, array $call): void
         $params = (array)$call['params'];
         $object = $call['object'] ?? null;
         $method = array_shift($params);
+        $not = false;
+        if (str_starts_with($method, '!')) {
+            $method = substr($method, 1);
+            $not = true;
+        } elseif (str_starts_with($method, 'not ')) {
+            $method = substr($method, 4);
+            $not = true;
+        }
+        $method = trim($method);
 
         if ($object && method_exists($object, $method)) {
             $value = $object->{$method}(...$params);
             if (is_array($value) && isset($field[$property]) && is_array($field[$property])) {
                 $value = $this->mergeArrays($field[$property], $value);
             }
-            $field[$property] = $value;
+            $field[$property] = $not ? !$value : $value;
         }
     }
 
diff --git a/system/src/Grav/Framework/Flex/FlexDirectoryForm.php b/system/src/Grav/Framework/Flex/FlexDirectoryForm.php
index e095a5d8f7..dff0836ba8 100644
--- a/system/src/Grav/Framework/Flex/FlexDirectoryForm.php
+++ b/system/src/Grav/Framework/Flex/FlexDirectoryForm.php
@@ -318,11 +318,11 @@ public function getFileUploadAjaxRoute(): ?Route
     }
 
     /**
-     * @param string $field
-     * @param string $filename
+     * @param string|null $field
+     * @param string|null $filename
      * @return Route|null
      */
-    public function getFileDeleteAjaxRoute($field, $filename): ?Route
+    public function getFileDeleteAjaxRoute($field = null, $filename = null): ?Route
     {
         return null;
     }
diff --git a/system/src/Grav/Framework/Flex/FlexForm.php b/system/src/Grav/Framework/Flex/FlexForm.php
index 3625189b20..aba0044f77 100644
--- a/system/src/Grav/Framework/Flex/FlexForm.php
+++ b/system/src/Grav/Framework/Flex/FlexForm.php
@@ -378,22 +378,28 @@ public function getFileUploadAjaxRoute(): ?Route
     {
         $object = $this->getObject();
         if (!method_exists($object, 'route')) {
-            return null;
+            /** @var Route $route */
+            $route = Grav::instance()['route'];
+
+            return $route->withExtension('json')->withGravParam('task', 'media.upload');
         }
 
         return $object->route('/edit.json/task:media.upload');
     }
 
     /**
-     * @param string $field
-     * @param string $filename
+     * @param string|null $field
+     * @param string|null $filename
      * @return Route|null
      */
-    public function getFileDeleteAjaxRoute($field, $filename): ?Route
+    public function getFileDeleteAjaxRoute($field = null, $filename = null): ?Route
     {
         $object = $this->getObject();
         if (!method_exists($object, 'route')) {
-            return null;
+            /** @var Route $route */
+            $route = Grav::instance()['route'];
+
+            return $route->withExtension('json')->withGravParam('task', 'media.delete');
         }
 
         return $object->route('/edit.json/task:media.delete');
diff --git a/system/src/Grav/Framework/Flex/FlexObject.php b/system/src/Grav/Framework/Flex/FlexObject.php
index fb4e59f36b..945f5adfed 100644
--- a/system/src/Grav/Framework/Flex/FlexObject.php
+++ b/system/src/Grav/Framework/Flex/FlexObject.php
@@ -71,6 +71,8 @@ class FlexObject implements FlexObjectInterface, FlexAuthorizeInterface
     /** @var array */
     private $_meta;
     /** @var array */
+    protected $_original;
+    /** @var array */
     protected $_changes;
     /** @var string */
     protected $storage_key;
@@ -370,7 +372,7 @@ public function exists(): bool
      */
     public function searchProperty(string $property, string $search, array $options = null): float
     {
-        $options = $options ?? $this->getFlexDirectory()->getConfig('data.search.options', []);
+        $options = $options ?? (array)$this->getFlexDirectory()->getConfig('data.search.options');
         $value = $this->getProperty($property);
 
         return $this->searchValue($property, $value, $search, $options);
@@ -384,7 +386,7 @@ public function searchProperty(string $property, string $search, array $options
      */
     public function searchNestedProperty(string $property, string $search, array $options = null): float
     {
-        $options = $options ?? $this->getFlexDirectory()->getConfig('data.search.options', []);
+        $options = $options ?? (array)$this->getFlexDirectory()->getConfig('data.search.options');
         if ($property === 'key') {
             $value = $this->getKey();
         } else {
@@ -441,6 +443,16 @@ protected function searchValue(string $name, $value, string $search, array $opti
         return 0;
     }
 
+    /**
+     * Get original data before update
+     *
+     * @return array
+     */
+    public function getOriginalData(): array
+    {
+        return $this->_original ?? [];
+    }
+
     /**
      * Get any changes based on data sent to update
      *
@@ -654,7 +666,8 @@ public function update(array $data, array $files = [])
             }
 
             // Store the changes
-            $this->_changes = Utils::arrayDiffMultidimensional($this->getElements(), $elements);
+            $this->_original = $this->getElements();
+            $this->_changes = Utils::arrayDiffMultidimensional($this->_original, $elements);
         }
 
         if ($files && method_exists($this, 'setUpdatedMedia')) {
diff --git a/system/src/Grav/Framework/Flex/Interfaces/FlexFormInterface.php b/system/src/Grav/Framework/Flex/Interfaces/FlexFormInterface.php
index 9539a154cc..32dab19680 100644
--- a/system/src/Grav/Framework/Flex/Interfaces/FlexFormInterface.php
+++ b/system/src/Grav/Framework/Flex/Interfaces/FlexFormInterface.php
@@ -38,8 +38,8 @@ public function getFileUploadAjaxRoute();
     /**
      * Get route for deleting files by AJAX.
      *
-     * @param string $field     Field where the file is associated into.
-     * @param string $filename  Filename for the file.
+     * @param string|null $field     Field where the file is associated into.
+     * @param string|null $filename  Filename for the file.
      * @return Route|null       Returns Route object or null if file uploads are not enabled.
      */
     public function getFileDeleteAjaxRoute($field, $filename);
diff --git a/system/src/Grav/Framework/Session/Session.php b/system/src/Grav/Framework/Session/Session.php
index ddab08d757..3feae5a2a5 100644
--- a/system/src/Grav/Framework/Session/Session.php
+++ b/system/src/Grav/Framework/Session/Session.php
@@ -338,23 +338,12 @@ public function invalidate()
     {
         $name = $this->getName();
         if (null !== $name) {
-            $params = session_get_cookie_params();
-
-            $cookie_options = array (
-                'expires'  => time() - 42000,
-                'path'     => $params['path'],
-                'domain'   => $params['domain'],
-                'secure'   => $params['secure'],
-                'httponly' => $params['httponly'],
-                'samesite' => $params['samesite']
-            );
-
             $this->removeCookie();
 
             setcookie(
                 session_name(),
                 '',
-                $cookie_options
+                $this->getCookieOptions(-42000)
             );
         }
 
@@ -463,27 +452,36 @@ protected function onSessionStart(): void
     }
 
     /**
-     * @return void
+     * Store something in cookie temporarily.
+     *
+     * @param int|null $lifetime
+     * @return array
      */
-    protected function setCookie(): void
+    public function getCookieOptions(int $lifetime = null): array
     {
         $params = session_get_cookie_params();
 
-        $cookie_options = array (
-            'expires'  => time() + $params['lifetime'],
+        return [
+            'expires'  => time() + ($lifetime ?? $params['lifetime']),
             'path'     => $params['path'],
             'domain'   => $params['domain'],
             'secure'   => $params['secure'],
             'httponly' => $params['httponly'],
             'samesite' => $params['samesite']
-        );
+        ];
+    }
 
+    /**
+     * @return void
+     */
+    protected function setCookie(): void
+    {
         $this->removeCookie();
 
         setcookie(
             session_name(),
             session_id(),
-            $cookie_options
+            $this->getCookieOptions()
         );
     }
 
diff --git a/system/src/Phive/Twig/Extensions/Deferred/DeferredExtension.php b/system/src/Phive/Twig/Extensions/Deferred/DeferredExtension.php
new file mode 100644
index 0000000000..3a41e4a0e2
--- /dev/null
+++ b/system/src/Phive/Twig/Extensions/Deferred/DeferredExtension.php
@@ -0,0 +1,70 @@
+<?php
+
+// Fix too many ob_get_clean() calls when exception is thrown inside the template.
+
+namespace Phive\Twig\Extensions\Deferred;
+
+class DeferredExtension extends \Twig_Extension
+{
+    /**
+     * @var array
+     */
+    private $blocks = array();
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getTokenParsers()
+    {
+        return array(new DeferredTokenParser());
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getNodeVisitors()
+    {
+        return array(new DeferredNodeVisitor());
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getName()
+    {
+        return 'deferred';
+    }
+
+    public function defer(\Twig_Template $template, $blockName)
+    {
+        ob_start();
+        $templateName = $template->getTemplateName();
+        $this->blocks[$templateName][] = [ob_get_level(), $blockName];
+    }
+
+    public function resolve(\Twig_Template $template, array $context, array $blocks)
+    {
+        $templateName = $template->getTemplateName();
+        if (empty($this->blocks[$templateName])) {
+            return;
+        }
+
+        while ($block = array_pop($this->blocks[$templateName])) {
+            [$level, $blockName] = $block;
+            if (ob_get_level() !== $level) {
+                continue;
+            }
+
+            $buffer = ob_get_clean();
+
+            $blocks[$blockName] = array($template, 'block_'.$blockName.'_deferred');
+            $template->displayBlock($blockName, $context, $blocks);
+
+            echo $buffer;
+        }
+
+        if ($parent = $template->getParent($context)) {
+            $this->resolve($parent, $context, $blocks);
+        }
+    }
+}