The Multiple Roles plugin for WordPress is vulnerable to Cross-Site Request Forgery in versions up to, and including, 1.3.1. This is due to missing or incorrect nonce validation on the mu_add_roles_in_signup_meta() and mu_add_roles_in_signup_meta_recently() functions. This makes it possible for unauthenticated attackers to add additional roles to users via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.