CVE-2026-30228: parse-server's file creation and deletion bypasses `readOnlyMasterKey` write restriction

The readOnlyMasterKey can be used to create and delete files via the Files API (POST /files/:filename, DELETE /files/:filename). This bypasses the read-only restriction which violates the access scope of the readOnlyMasterKey.

Any Parse Server deployment that uses readOnlyMasterKey and exposes the Files API is affected. An attacker with access to the readOnlyMasterKey can upload arbitrary files or delete existing files.