The WP Helper Premium WordPress plugin before 4.7.6 does not verify the order key when rendering its custom order confirmation page or when handling the related AJAX actions, allowing unauthenticated users to view other customers' order details, including personal information, as well as change the state of arbitrary orders.
Exploitation requires WooCommerce to be active and the WP Helper Premium WordPress plugin before 4.7.6's optional order confirmation page module to be enabled.