The Biagiotti Membership plugin for WordPress is vulnerable to authentication bypass in all versions up to, and including, 1.0.2. This is due to the plugin not properly verifying a users identity prior to authenticating them. This makes it possible for unauthenticated attackers to log in as other users, such as administrators, granted they have access to an email.
When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.