ApostropheCMS: POST /api/v1/@apostrophecms/doc/slugTaken discloses existence of private/admin-only content to any authenticated user

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

# 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.