SUMIT Payment Gateway for WooCommerce < 4.0.0 - Unauthenticated Payment Confirmation Forgery via Redirect Callback

The SUMIT Payment Gateway for WooCommerce WordPress plugin before 4.0.0 does not bind the payment it confirms with the provider to the order being completed, nor check the payment amount against the order total, allowing unauthenticated users to mark a pending order as paid by replaying a payment identifier obtained from any single genuine payment.