WordPress GiveWP plugin before 2.17.3 contains a cross-site scripting vulnerability. The plugin does not sanitize and escape the form_id parameter before returning it in the response of an unauthenticated request via the give_checkout_login AJAX action. An attacker can inject arbitrary script in the browser of a user in the context of the affected site. This can allow the attacker to steal cookie-based authentication credentials and launch other attacks.