CVE-2026-53663: React Router: Potential CSRF via PUT/PATCH/DELETE document requests

Certain CSRF checks in React Router v7 Framework Mode were insufficient and run on POST requests, but were bypassed on PUT/PATCH/DELETE requests. This is a low severity vulnerability because modern browser protections (CORS preflight, SameSite cookies) already block the cross-origin attack vectors that this missing CSRF check would otherwise gate.

[!NOTE] This does not impact your React Router application if you are using Declarative Mode (<BrowserRouter>) or Data Mode (createBrowserRouter/<RouterProvider>).