The UserPlus plugin for WordPress is vulnerable to unauthorized access, modification, and loss of data due to a missing capability check on multiple functions in all versions up to, and including, 2.0. This makes it possible for authenticated attackers with subscriber-level permissions or above, to add, modify, or delete user meta and plugin options.
https://plugins.trac.wordpress.org/browser/userplus/trunk/admin/admin-ajax.php?rev=1627771#L225
https://plugins.trac.wordpress.org/browser/userplus/trunk/admin/admin-ajax.php?rev=1627771#L216
https://plugins.trac.wordpress.org/browser/userplus/trunk/admin/admin-ajax.php?rev=1627771#L186