The WPBookit plugin for WordPress is vulnerable to privilege escalation via account takeover in all versions up to, and including, 1.0.2. This is due to the plugin not properly validating a user's identity prior to updating their details like password and email through the edit_profile_data() function. This makes it possible for unauthenticated attackers to change arbitrary user's email addresses and passwords, including administrators, and leverage that to gain access to their account.
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.