CVE-2026-88060: Angular: SSR XSS via Unescaped <template> Content Across DocumentFragment Boundaries in Fallback Raw-Content Elements

An XSS vulnerability exists in @angular/platform-server during server-side rendering (SSR) HTML serialization when traversing ancestor tags across <template> element boundaries. When an application renders untrusted user input within raw-text tags (<xmp>, <style>, <script>), comments, or text nodes inside a <template> that is nested within a fallback raw-content element (<noscript>, <iframe>, <noembed>, <noframes>), matching closing tags (e.g., </noscript>) are not escaped during HTML serialization. When rendered in a browser, this unescaped closing tag prematurely terminates the fallback container and executes trailing markup as active DOM elements.