fix: parse Referrer-Policy as comma-separated list per W3C spec#86
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dmchaledev wants to merge 1 commit into
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fix: parse Referrer-Policy as comma-separated list per W3C spec#86dmchaledev wants to merge 1 commit into
dmchaledev wants to merge 1 commit into
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The W3C Referrer Policy spec allows the header value to be a comma-separated list of tokens; browsers use the last recognised value and skip any unrecognised tokens. The previous implementation compared the raw header string directly against the strong-value allowlist, so a valid multi-value header like: Referrer-Policy: no-referrer-when-downgrade, strict-origin-when-cross-origin was incorrectly scored as 5/10 (warning) instead of 10/10 (good), producing false positives in security audits. Fix: split on commas, reverse, and find the last recognised policy token (matching browser behaviour). Adds three new tests covering the multi-value cases. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01J7KzZTM9SxvFYPJFbe3qRq
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Summary
The
checkReferrerPolicyfunction was comparing the raw header string directly against the strong-value allowlist, which broke for comma-separated multi-value headers.Root cause: The W3C Referrer Policy spec allows the
Referrer-Policyheader to contain a comma-separated list of policy tokens. Browsers parse the list left-to-right and use the last recognised token (unrecognised tokens are skipped as a forwards-compatibility mechanism). The old code treated the full raw string as a single value, so a perfectly valid header like:was scored 5/10 (warning) instead of the correct 10/10 (good), producing false positives in security audits.
Fix: Split on commas, reverse the token list, and find the first recognised policy token — exactly the same last-recognised-wins logic browsers use. Single-value headers behave identically to before.
Changes
src/rules.ts— updatedcheckReferrerPolicyto apply last-recognised-token semantics for comma-separated header valuestest/analyzer.test.ts— added 3 new test cases:good(10/10)warning(5/10)good(10/10)All 88 tests pass.
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