The Visma Pay for WooCommerce WordPress plugin before 1.2.2 does not verify the authenticity of...

The Visma Pay for WooCommerce WordPress plugin before 1.2.2 does not verify the authenticity of payment gateway return requests, relying on a merchant secret that is empty on a store which has not entered its credentials, allowing unauthenticated attackers to mark arbitrary orders as paid and to disclose the name, email address and postal address of any order's customer.