GHSA-f66c-mpj2-3r8h

### Summary The `slugTaken` endpoint returns a boolean indicating whether a slug is in use across all document types and visibility levels, with no permission or type filter. Any logged-in user (including editors) can enumerate the slug space of private pages, drafts, and archived content. ### Details `POST /api/v1/@apostrophecms/doc/slugTaken` with body `{ "slug": "target-slug" }` runs a raw existence check against the documents collection. It does not: - Check whether the requesting user has read permission for documents of that type. - Filter by `visibility` (public, loginRequired, private). - Filter by `viewRole`. - Filter by publication status (draft vs published). A single authenticated session can iterate the slug space to enumerate the full content inventory of the CMS, including content the user is explicitly prohibited from viewing. ### PoC ```bash # Any authenticated session works — editor role sufficient curl -b "$EDITOR_JAR" -X POST \ -H "Content-Type: application/json" \ -d '{"slug":"known-private-page-slug"}' \ "http://TARGET/api/v1/@apostrophecms/doc/slugTaken" # → { "taken": true } — confirms private page exists curl -b "$EDITOR_JAR" -X POST \ -H "Content-Type: application/json" \ -d '{"slug":"zzz-nonexistent"}' \ "http://TARGET/api/v1/@apostrophecms/doc/slugTaken" # → { "taken": false } ``` ### Impact Information disclosure. An attacker with any authenticated session can enumerate all slugs in the system, mapping the full content structure of the CMS including private and admin-only content.