The UserPro plugin for WordPress is vulnerable to privilege escalation in versions up to, and including, 3.6.0 due to the insecure 'administrator' default value for the 'default_user_role' option. This makes it possible for unauthenticated attackers to register an administrator user even if the registration form is disabled.
A product incorrectly assigns a privilege to a particular actor, creating an unintended sphere of control for that actor.