Advantech WISE-DeviceOn Server versions prior to 5.4 contain a stored cross-site scripting (XSS) vulnerability in the /rmm/v1/plugin-config/addins/menus endpoint. When an authenticated user adds or edits an AddIns menu entry, the label and path values are stored in plugin configuration data and later rendered in the AddIns UI 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 AddIns entry, potentially enabling session compromise and unauthorized actions as the victim.