The Tutor LMS – eLearning and online course solution plugin for WordPress is vulnerable to DOM-Based Cross-Site Scripting via the 'redirect_url' parameter in versions up to, and including, 4.0.8 This is due to insufficient input validation in the Topbar component's back button handler. This makes it possible for unauthenticated attackers to inject arbitrary web scripts that execute in the victim's browser whenever the victim accesses a page that includes the malicious payload.