RomM (ROM Manager) allows users to scan, enrich, browse and play their game collections with a clean and responsive interface. Prior to 4.4.1 and 4.4.1-beta.2, users can read private collections / smart collections belonging to other users by directly accessing their IDs via API. No ownership verification or checking if the collection is public/private before returning collection data. This vulnerability is fixed in 4.4.1 and 4.4.1-beta.2.