GHSA-4m4j-hmqq-3gxm symfony/ux-live-component: CSRF Protection Bypass — Accept Header is CORS-Safelisted

• Packagist symfony/ux-live-component: >= 2.22.0, < 2.36.0 → fixed in 2.36.0 • Packagist symfony/ux-live-component: >= 3.0.0, < 3.1.0 → fixed in 3.1.0

Description When using `symfony/ux-live-component`, methods annotated with `#[LiveAction]` are invokable from the browser and mutate server-side state via AJAX. `Symfony\UX\LiveComponent\EventListener\LiveComponentSubscriber::isLiveComponentRequest()` gated these invocations on the presence of `Accept: application/vnd.live-component+html`, with a code comment stating that this acted as a CSRF protection. The `Accept` header is a CORS-safelisted request header, so a cross-origin `fetch()` can set it without triggering a preflight. The header therefore provided no CSRF protection. Any `#[LiveAction]` could be forged cross-origin against a victim's session. In practice the attack is mitigated by `SameSite=Lax` session cookies (Symfony's default), but applications using `SameSite=None`, `credentials: 'include'` with a permissive cookie policy, or that have been pivoted from another same-origin vector remained exposed. Resolution `isLiveComponentRequest()` now additionally requires the request header `X-Requested-With: XMLHttpRequest`. This header is not CORS-safelisted, so the browser issues a preflight `OPTIONS` request for any cross-origin attempt; Symfony does not advertise CORS for LiveComponent endpoints, the preflight fails, and the real request is blocked before it reaches the application. The bundled Stimulus client already sends `X-Requested-With` on every LiveComponent request (`RequestBuilder.ts`), so standard usage is unaffected. Cross-origin callers must add `X-Requested-With` to their CORS `Access-Control-Allow-Headers` allow-list. The patch for this issue is available here for branch 2.x (and forward-ported to 3.x). Credits Symfony would like to thank Anthropic (via Project Glasswing) for reporting the issue and Hugo Alliaume for providing the fix.