Overview
About vulnerability
A Cross-Site Scripting (XSS) vulnerability exists in @angular/platform-server’s DOM emulation dependency (domino) when serializing the content of <noscript> elements.
When rendering dynamic text content inside a <noscript> element via template bindings (such as {{ value }} or [textContent]), the template engine expects the browser to render the content safely. Under Server-Side Rendering (SSR), domino is configured with scripting enabled, meaning <noscript> is treated as a raw-text element.
However, domino’s serializer completely omitted <noscript> from the list of raw-text elements requiring closing-tag escaping during DOM serialization. As a result, any occurrence of </noscript> in the bound dynamic text was never escaped under any circumstances.
The unescaped closing tag was serialized directly into the output HTML (e.g. <noscript></noscript><script>alert(1)</script></noscript>). When parsed by a browser, it closes the <noscript> block early, allowing the injected <script> block to execute in the user’s browser context, causing same-origin Cross-Site Scripting (XSS).
Impact
This vulnerability allows an attacker to perform same-origin Cross-Site Scripting (XSS) attacks against any user visiting an SSR-rendered page that binds user-controlled data inside a <noscript> element. This can lead to session hijacking, credentials theft, unauthorized actions on behalf of users, and defacement.
Patched Versions
- 22.0.0-rc.2
- 21.2.16
- 20.3.24
- 19.2.25
Workarounds
If you cannot immediately update your dependencies, you can:
- Avoid binding user-controlled values inside
<noscript>elements. - Sanitize any user input placed inside
<noscript>to explicitly strip closing</noscript>tags before passing it to the template.
Details
- Affected product:
- Angular , AngularJS , ng-packagr , nguniversal
- Affected packages:
- @angular/animations @ 8.0.0 (+906 more)