WP Users Masquerade <= 2.0.0 - Authenticated (Subscriber+) Authentication Bypass

The WP Users Masquerade plugin for WordPress is vulnerable to authentication bypass in versions up to, and including, 2.0.0. This is due to incorrect authentication and capability checking in the 'ajax_masq_login' function. This makes it possible for authenticated attackers, with subscriber-level permissions and above, to log in as any existing user on the site, such as an administrator.