The Ultimate Member – User Profile, Registration, Login, Member Directory, Content Restriction & Membership Plugin plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 2.8.6. This is due to missing or incorrect nonce validation on the admin_init or user_action_hook function. This makes it possible for unauthenticated attackers to modify a users membership status via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.