The openml/openml.org web application version v2.0.20241110 uses incremental user IDs and insufficient email ownership verification during email update workflows. An authenticated attacker controlling a user account with a lower user ID can update their email address to that of another user with a higher user ID without proper verification. This results in the victim's email being reassigned to the attacker's account, causing the victim to be locked out immediately and unable to log in. The vulnerability leads to denial of service via account lockout but does not grant the attacker direct access to the victim's private data.