Simple Membership < 4.7.8 - Unauthenticated Stored XSS via PayPal Subscription Subscriber Name

The Simple Membership WordPress plugin before 4.7.8 does not sanitise a subscriber name value received from an unauthenticated payment approval request, nor escape it when displaying it in the administration dashboard, allowing unauthenticated attackers to store arbitrary JavaScript that executes in an administrator's session.