Uptime Kuma's Matomo analytics integration (server/analytics/matomo-analytics.js) injects the admin-configurable Matomo "siteId" value as a bare, unquoted JavaScript expression inside a <script> block rendered on every public status page: "_paq.push(['setSiteId', ${escapedSiteIdHTMLAttribute}]);". The escaping pipeline used (jsesc with isScriptContext:true, then html-escaper.escape()) does not escape the characters "]", ")", ";", "(", which are sufficient to break out of the array/push expression context. A siteId value such as "1]);alert(document.cookie)//", once saved by an editor/admin, executes arbitrary JavaScript for every unauthenticated visitor of the public /status/<slug> page, enabling session-cookie theft and full page takeover.