Nextcloud is an open source content collaboration platform. Prior to version 2.7.2, authenticated users can check if arbitrary files are associated with specific approval workflows where they can request approval. This issue has been patched in version 2.7.2.
https://hackerone.com/reports/3475210
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-h7gm-vgxr-9hcw