phpMyFAQ: Attachment download allowed without dlattachment right (broken access control)

Summary

A logged‑in user without the dlattachment right can download FAQ attachments. This is due to a permissive permission check in attachment.php that treats the mere presence of a right key as authorization and a flawed group/user logic expression.

Details

In attachment.php, the access decision uses: ($groupPermission || ($groupPermission && $userPermission)) && isset($permission['dlattachment']) isset() returns true even when the right value is false, and the logic simplifies to $groupPermission for some permission modes. As a result, a user without dlattachment can still access the attachment.

PoC

Precondition: A non‑admin user exists; an attachment is associated to a FAQ record; records.allowDownloadsForGuests = false. Log in as a non‑admin user without dlattachment. Request the attachment download endpoint.

curl -c /tmp/pmf_api_cookies.txt \
  -H 'Content-Type: application/json' \
  -d '{"username":"tester","password":"Test1234!"}' \
  http://192.168.40.16/phpmyfaq/api/v3.0/login

curl -i -b /tmp/pmf_api_cookies.txt \
  "http://192.168.40.16/phpmyfaq/index.php?action=attachment&id=1"

Impact

Unauthorized users can download attachments (confidentiality breach). Depending on content, this may expose sensitive documents.