parse-server's file creation and deletion bypasses `readOnlyMasterKey` write restriction

Impact

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.

Patches

The fix adds permission checks to both the file upload and file delete handlers.

Workarounds

There is no workaround other than not using readOnlyMasterKey, or restricting network access to the Files API endpoints.

References

• GitHub security advisory: https://github.com/parse-community/parse-server/security/advisories/GHSA-xfh7-phr7-gr2x
• Fix for Parse Server 9: https://github.com/parse-community/parse-server/releases/tag/9.5.0-alpha.3
• Fix for Parse Server 8: https://github.com/parse-community/parse-server/releases/tag/8.6.5