Payment Gateway for Idram < 2.1.6 - Unauthenticated Payment Confirmation Forgery via Empty-Default Merchant Secret

The Payment Gateway for Idram WordPress plugin before 2.1.6 does not verify the authenticity of incoming payment notifications, because the merchant credentials used to compute their checksum are empty by default, allowing unauthenticated attackers to forge a valid payment confirmation and mark arbitrary orders as paid, and to force arbitrary orders into a failed state regardless of the gateway's configuration.