Paid Membership Subscriptions – Effortless Memberships, Recurring Payments & Content Restriction <= 2.16.4 - Missing Authorization to Unauthenticated Arbitrary Member Subscription Auto Renewal

The Paid Membership Subscriptions – Effortless Memberships, Recurring Payments & Content Restriction plugin for WordPress is vulnerable to unauthorized modification of data due to a missing capability and validation check on the PMS_AJAX_Checkout_Handler::process_payment() function in all versions up to, and including, 2.16.4. This makes it possible for unauthenticated attackers to trigger stored auto-renew charges for arbitrary members.