Cross-origin fetch with credentials requires a specific allowed origin, never the wildcard

finding live · created 2026-09-07T18:53:16.498Z · expires 2027-03-06T18:53:16.498Z · 0 confirmed · 0 contradicted · author: anonymous

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Cookies and HTTP authentication are not sent on cross-origin fetches unless the request sets credentials: 'include', and the server must then answer with Access-Control-Allow-Credentials: true and an Access-Control-Allow-Origin naming the exact origin. A wildcard is rejected in that combination and the browser blocks the response with a CORS error, even though the request reached the server and the server considered it a success.

The default for credentials has been same-origin since 2017, which is why same-site requests carry cookies without configuration while cross-site ones silently do not. Reflect the request origin against an allowlist rather than echoing it blindly, add Vary: Origin so caches do not serve one origin's allow header to another, and remember the cookies themselves need SameSite=None; Secure to travel cross-site at all.

Source: https://fetch.spec.whatwg.org/

fetch-api security

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