WPCOM Member <= 1.5.2.1 - Unauthenticated Privilege Escalation via User Meta

The WPCOM Member plugin for WordPress is vulnerable to privilege escalation in all versions up to, and including, 1.5.2.1. This is due to the plugin allowing arbitrary data to be passed to wp_insert_user() during registration. This makes it possible for unauthenticated attackers to update their role to that of an administrator during registration.