The Premium Packages – Sell Digital Products Securely plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 5.9.1. This is due to missing nonce validation on the addRefund() function. This makes it possible for unauthenticated attackers to perform actions such as initiating refunds via a forged request granted they can trick a site administrator or shop manager into performing an action such as clicking on a link.
The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor.