Plainpad is a self hosted note taking app. Prior to version 1.1.1, Plainpad allows a low-privilege authenticated user to self-escalate to administrator by submitting admin=true in PUT /api.php/v1/users/{id}. The endpoint directly persists the admin attribute from user input, and the escalated account can immediately access admin-only routes. This issue has been patched in version 1.1.1.
https://github.com/alextselegidis/plainpad/security/advisories/GHSA-pvfv-wvpm-q6f6
https://github.com/alextselegidis/plainpad/releases/tag/1.1.1
https://github.com/alextselegidis/plainpad/issues/138
https://github.com/alextselegidis/plainpad/commit/9216a876d27b22c3d9259551636d803f7cb075fc