The vulnerability stems from the access control flow in findusers.php that first checks for a valid security token (lines 20-23) before checking admin status. Since tokens can be obtained without authentication (e.g., via misc.php), this allows unauthenticated attackers to bypass the intended access controls. The GitHub advisory and external analysis confirm this specific file's logic was patched in 1.4.3 by adding proper authentication checks alongside token validation.