This is GScan.

A lightweight Chromium-based extension that scans Gmail email messages for malicious links using urlscan.io.

Note that this will only return the urlscan.io verdict result.

Compatibility:

• Chromium browsers (e.g. Google Chrome, Opera, etc.)
• Gmail webmail (mail.google.com)
• urlscan.io account required

Instructions:

1. Download the entirety of the GScan folder.
2. Enable developer mode on your Chromium browser of choice and upload the extension as an unpacked extension.
3. Create an account on urlscan.io and generate an API key. Copy this key.
4. Click the options menu in the extension's settings and paste the API key. Press save.
5. Load an email in Gmail with the extension active.
6. Click on the extension and follow the prompts.