Nginx UI is a web user interface for the Nginx web server. From 2.0.0 until 2.5.0, the self-upgrade mechanism validates a downloaded binary only with a same-origin digest obtained from the same upgrade mirror. A compromised mirror or network attacker able to alter both responses can supply a malicious executable and matching digest. An operator-triggered upgrade is required, and the application installs and runs the attacker-controlled code in the Nginx UI process context on the next upgrade. This issue is fixed in version 2.5.0.