The Sadad QA Payment WordPress plugin through 1.28 does not correctly verify the authenticity of incoming payment notifications, as the verification is keyed on a merchant secret that is empty by default and the rest of the signed data is attacker-controlled, allowing unauthenticated attackers to forge a valid confirmation and mark orders as paid without payment.
https://wpscan.com/vulnerability/0681f5a8-a1cd-44b0-b7c8-c3eacbd9e96a/