The Payex Payment Gateway for Woocommerce WordPress plugin through 1.2.10 does not properly verify the authenticity of incoming payment notifications, relying on a validation secret that is empty by default, allowing unauthenticated attackers to forge a valid payment confirmation and mark any order as paid.
https://wpscan.com/vulnerability/d8667422-5fcf-4904-8383-e5f601399153/