Only send the document security headers on documents - #1839
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content_types defaulted to an empty list for both the CSP and clickjacking listeners, which means "every content type", so every JSON API response carried the full ~600 byte Content-Security-Policy and an X-Frame-Options header. The security advisory and download tracking endpoints alone account for around 4.5M responses per APM period. Neither header does anything for a non-document response: CSP governs document loading and X-Frame-Options governs framing, and a JSON body is neither. Restricting both listeners to text/html is route-drift-proof, unlike enumerating API path prefixes.
stof
approved these changes
Sep 7, 2026
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content_typesdefaulted to an empty list for both the CSP and clickjacking listeners, which nelmio treats as "every content type" (AbstractContentTypeRestrictableListener::isContentTypeValid). So every JSON API response carried the full ~600 byteContent-Security-Policyplus anX-Frame-Optionsheader. The security-advisory and download-tracking endpoints alone account for ~4.5M responses per APM period.Neither header does anything for a non-document response: CSP governs document loading and
X-Frame-Optionsgoverns framing, and a JSON body is neither.Restricting both listeners to
text/htmlis route-drift-proof, unlike enumerating API path prefixes inclickjacking.paths— new endpoints are covered automatically, and HTML pages are unaffected.Verification
composer phpstanclean, full suite green. NewSecurityHeadersTestasserts both halves: an HTML page still getsX-Frame-Options: DENYand a CSP, and/packages/list.jsongets neither. Confirmed the JSON assertion fails against the previous config, so it isn't vacuous.