The Tutor LMS – eLearning and online course solution plugin for WordPress is vulnerable to Insecure Direct Object Reference in all versions up to, and including, 4.0.8 via the 'student_id' parameter due to missing validation on a user controlled key. This makes it possible for authenticated attackers, with subscriber-level access and above, to disclose the email address and Tutor profile phone number of arbitrary WordPress users, including Administrators, by iterating over user IDs via the student_id parameter.