fix(api): strip stale Access-Control-Allow-Origin in addCorsHeaders - #431
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…ddCorsHeaders Follow-up to #427. addCorsHeaders re-applied corsHeadersFor via Headers.set, but when the evaluated origin is not allowed no ACAO is computed, so a stale/upstream Access-Control-Allow-Origin (and Allow-Credentials) survived on the response and could leak. Delete both CORS headers before re-applying, guaranteeing at most one correct value and no ACAO for disallowed origins.
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Follow-up (MED) to #427 (
352412d).Problem
addCorsHeadersre-appliedcorsHeadersForwithHeaders.set, but when the evaluated origin is not allowed, noAccess-Control-Allow-Originis computed — so a stale/upstream ACAO (andAccess-Control-Allow-Credentials) already on the response survived and could leak an old origin.Fix
Delete
Access-Control-Allow-OriginandAccess-Control-Allow-Credentialsfrom the response headers before applying the computed CORS headers. Guarantees at most one correct value and no ACAO for disallowed origins (secure by default).Tests
Added unit tests to
cors.test.ts:Verified the new leak tests fail on the pre-fix code and pass after.
Verification
tsc --noEmit: clean