The ARMember plugin for WordPress is vulnerable to Cross-Site Request Forgery in versions up to, and including, 4.0.5. This is due to missing or incorrect nonce validation on the arm_check_user_cap function. This makes it possible for unauthenticated attackers to perform multiple unauthorized actions via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.
https://plugins.trac.wordpress.org/changeset/2932691/armember-membership/trunk/autoload.php