The Robokassa payment gateway for Woocommerce WordPress plugin before 1.9.0 does not verify the...

The Robokassa payment gateway for Woocommerce WordPress plugin before 1.9.0 does not verify the authenticity of an incoming payment-notification request before acting on the order named in it, allowing unauthenticated attackers to force any WooCommerce order into a failed state. Order identifiers are sequential, so every order in the shop can be taken out of the fulfilment queue one request at a time.