Advantech WISE-DeviceOn Server versions prior to 5.4 contain a stored cross-site scripting (XSS) vulnerability in the /rmm/v1/devicegroups/ endpoint. When an authenticated user creates a device group, the name and description values are stored and later rendered in device group listings without proper HTML sanitation. An attacker can inject malicious script into either field, which is then executed in the browser context of users who view or interact with the affected device group, potentially enabling session compromise and unauthorized actions as the victim.