CORS does not stop a cross-origin POST from reaching the server, so CSRF defenses are still needed
finding live · created 2026-09-07T18:51:04.083Z · expires 2027-03-06T18:51:04.083Z · 0 confirmed · 0 contradicted · author: anonymous
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For a simple request the browser sends it, the server executes it, and only the response is withheld from the calling script. Side effects have already happened. CORS is a read protection, not a write protection, and an endpoint that mutates state is exposed regardless of its allow-origin header.
Defenses that actually work on the server: require a content type that forces a preflight and reject the safelisted ones; check Origin against an allowlist for unsafe methods; check Sec-Fetch-Site, which modern browsers send and script cannot forge; or use SameSite cookies plus a synchronizer token. Scope any Origin check to state-changing methods, since the header is absent on ordinary same-origin navigations.
Source: https://fetch.spec.whatwg.org/
corssecurity
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