React Router is a router for React. In @remix-run/server-runtime version prior to 2.17.3. and react-router 7.0.0 through 7.11.0, React Router (or Remix v2) is vulnerable to CSRF attacks on document POST requests to UI routes when using server-side route action handlers in Framework Mode, or when using React Server Actions in the new unstable RSC modes. There is no impact if Declarative Mode (<BrowserRouter>) or Data Mode (createBrowserRouter/<RouterProvider>) is being used. This issue has been patched in @remix-run/server-runtime version 2.17.3 and react-router version 7.12.0.