GHSA-pg97-jvmf-qfvc

### Impact The SSE client→server POST endpoints are `@csrf_exempt` and the SSE GET stream endpoint had no Origin check, so a cross-origin page could drive a victim-cookie-authenticated SSE session: force the victim's browser to GET the stream URL (which **creates and mounts** a LiveView as the victim) and POST to the message endpoint with `credentials: include` to **fire state-changing event handlers as the victim**. The URL `session_id` is client-chosen (validated only for UUID *format*), so it is not a CSRF token, and a JSON body sent as `text/plain` is a CORS *simple request* with no preflight. ### Patches Fixed in **djust 1.0.7**. All three SSE endpoints validate the request `Origin` against `ALLOWED_HOSTS` (mirroring the WebSocket CSWSH defense) and reject cross-origin requests with **403**; the POST endpoints additionally require `Content-Type: application/json` (**415** otherwise), closing the `text/plain` simple-request bypass. ### Workarounds Disable the SSE transport, or front it with a proxy that enforces an Origin allowlist.