Domoticz versions prior to 2026.3 contain a stored cross-site scripting (XSS) vulnerability in the mobile dashboard. Authenticated attackers can inject arbitrary HTML and JavaScript by updating Text or Alert subtype device values via the API. The mobile dashboard renders this data using ng-bind-html with only an nl2br() transform, which does not escape HTML, allowing malicious scripts to execute in administrator browsers. This can lead to session cookie theft and account takeover.