The Ultimate Member – User Profile, Registration, Login, Member Directory, Content Restriction & Membership Plugin plugin for WordPress is vulnerable to Sensitive Information Exposure in all versions up to, and including, 2.11.0 via the ajax_get_members function. This is due to the use of a predictable low-entropy token (5 hex characters derived from md5 of post ID) to identify member directories and insufficient authorization checks on the unauthenticated AJAX endpoint. This makes it possible for unauthenticated attackers to extract sensitive data including usernames, display names, user roles (including administrator accounts), profile URLs, and user IDs by enumerating predictable directory_id values or brute-forcing the small 16^5 token space.