The User Private Files – WordPress File Sharing Plugin plugin for WordPress is vulnerable to Insecure Direct Object Reference in all versions up to, and including, 2.1.0 via the 'dpk_upvf_update_doc' due to missing validation on the 'docid' user controlled key. This makes it possible for authenticated attackers, with subscriber-level access and above, to gain access to other user's private files.
The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.