User enumeration is found in in PHP Jabbers Time Slots Booking Calendar v3.3. This issue occurs during password recovery, where a difference in messages could allow an attacker to determine if the user is valid or not, enabling a brute force attack with valid users.
In PHP Jabbers Time Slots Booking Calendar 3.3 , lack of verification when changing an email address and/or password (on the Profile Page) allows remote attackers to take over accounts.