Vulnerability Instance

Angular Stored XSS Vulnerability via SVG Animation, SVG URL and MathML Attributes
A **Stored Cross-Site Scripting ([XSS](https://angular.dev/best-practices/security#preventing-cross-site-scripting-xss))** vulnerability has been identified in the **Angular Template Compiler**. It occurs because the compiler's internal security schema is incomplete, allowing attackers to bypass Angular's built-in security sanitization. Specifically, the schema fails to classify certain URL-holding attributes (e.g., those that could contain [`javascript:` URLs](https://developer.mozilla.org/en-US/Web/URI/Reference/Schemes/javascript)) as requiring strict URL security, enabling the injection of malicious scripts.

Additionally, a related vulnerability exists involving SVG animation elements (`<animate>`, `<set>`, `<animateMotion>`, `<animateTransform>`). The `attributeName` attribute on these elements was not properly validated, allowing attackers to dynamically target security-sensitive attributes like `href` or `xlink:href` on other elements. By binding `attributeName` to "href" and providing a `javascript:` URL in the `values` or `to` attribute, an attacker could bypass sanitization and execute arbitrary code.

Attributes confirmed to be vulnerable include:
*   SVG-related attributes: (e.g., `xlink:href`), and various MathML attributes (e.g., `math|href`, `annotation|href`).
*   SVG animation `attributeName` attribute when bound to "href" or "xlink:href".

When template binding is used to assign untrusted, user-controlled data to these attributes (e.g., `[attr.xlink:href]="maliciousURL"` or `<animate [attributeName]="'href'" [values]="maliciousURL">`), the compiler incorrectly falls back to a non-sanitizing context or fails to block the dangerous attribute assignment. This allows an attacker to inject a `javascript:URL` payload. Upon user interaction (like a click) on the element, or automatically in the case of animations, the malicious JavaScript executes in the context of the application's origin.