The Watu Quiz plugin for WordPress is vulnerable to Sensitive Information Exposure in all versions up to, and including, 3.4.1 via the watu-userinfo shortcode. This makes it possible for authenticated attackers, with contributor-level access and above, to extract sensitive user meta data which can include session tokens and user emails.
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.