The CryptoCloud WordPress plugin from 3.0.0 through 3.0.1 does not verify the authenticity of the payment notifications received by its gateway callback, as the integrity check is skipped while the webhook secret is left at its empty default, allowing unauthenticated attackers to mark arbitrary orders as paid or failed without any payment being made.
https://wpscan.com/vulnerability/fd5563ed-85c6-4b17-acf6-bdc2cd77dd4b/