In the dynamic landscape of web development, frameworks like Angular are indispensable, powering countless applications with their robust features. However, even the most sophisticated systems can harbor critical vulnerabilities. A recent discovery of a stored Cross-Site Scripting (XSS) flaw within Angular’s template compiler has sent ripples through the cybersecurity community. This vulnerability, tracked as CVE-2025-66412, presents a significant risk, allowing attackers to execute arbitrary malicious code by leveraging weaponized SVG animation files.

Understanding the Angular XSS Vulnerability (CVE-2025-66412)

The core of this vulnerability lies within Angular’s template compiler. Specifically, an incomplete security schema fails to adequately classify and sanitize URL-holding attributes within Scalable Vector Graphics (SVG) animation files. This oversight allows attackers to bypass Angular’s otherwise robust built-in security sanitization mechanisms. By embedding malicious JavaScript within attributes that are typically designed to hold URLs (like those found in SVG animations), an attacker can achieve Stored XSS.

When a vulnerable Angular application processes and renders these weaponized SVG animation files, the embedded malicious code executes within the user’s browser, in the context of the application. This gives the attacker the ability to:

• Steal sensitive user data, such as session cookies or login credentials.
• Deface websites or inject malicious content.
• Redirect users to phishing sites.
• Perform actions on behalf of the user, leading to account compromise.

Impact on Angular Applications

The severity of this vulnerability is high due to its ability to facilitate arbitrary code execution. Applications utilizing Angular versions below 19.2.17, 20.3.15, or 21.0.2 are susceptible. This broad range of affected versions means a significant number of existing Angular applications could be at risk if not promptly updated. The fact that it’s a Stored XSS makes it particularly dangerous, as the malicious payload persists on the server and is delivered to unsuspecting users whenever they access the affected content.

Weaponizing SVG Animation Files

SVG (Scalable Vector Graphics) is an XML-based vector image format for two-dimensional graphics with support for interactivity and animation. Animation attributes within SVG files, such as those used for defining movement or transformations, are the vectors for this attack. When Angular’s template compiler fails to properly sanitize these attributes, an attacker can craft an SVG file containing malicious JavaScript. This file, when processed by the vulnerable Angular application, triggers the XSS vulnerability, leading to the execution of the attacker’s code.

Remediation Actions

Mitigating this critical vulnerability requires immediate attention from developers and system administrators. Here are the essential steps:

• Update Angular: The most crucial step is to upgrade your Angular applications to patched versions. Specifically, ensure your application is running Angular 19.2.17, 20.3.15, 21.0.2, or higher. These versions contain the fix for CVE-2025-66412.
• Input Validation and Output Encoding: While Angular’s built-in sanitization is generally robust, this incident highlights the importance of layering security. Always perform rigorous input validation on any user-supplied content, especially when it involves file uploads or dynamic data loading. Additionally, ensure proper output encoding when rendering user-generated content, though relying solely on this might not be sufficient for complex SVG structures.
• Content Security Policy (CSP): Implement a strict Content Security Policy (CSP) where possible. A well-configured CSP can significantly reduce the impact of XSS attacks by restricting the sources of executable scripts, stylesheets, and other content.
• Security Audits and Code Reviews: Regularly conduct security audits and code reviews, particularly for sections of your application that handle user-generated content or process external files.

Tools for Detection and Mitigation

Integrating security tools into your development and deployment pipeline can help detect and mitigate such vulnerabilities.

Tool Name	Purpose	Link
OWASP ZAP	Dynamic Application Security Testing (DAST) for finding XSS and other web vulnerabilities.	https://www.zaproxy.org/
Burp Suite	Comprehensive web vulnerability scanner and penetration testing tool.	https://portswigger.net/burp
SonarQube	Static Application Security Testing (SAST) for code quality and security analysis.	https://www.sonarsource.com/products/sonarqube/
WhiteSource Bolt (or similar SCA)	Software Composition Analysis (SCA) to identify vulnerabilities in open-source components, including Angular.	https://www.whitesourcesoftware.com/freesolution

Conclusion

The discovery of CVE-2025-66412 serves as a stark reminder that even widely used and well-maintained frameworks like Angular can have deeply rooted security flaws. Developers must prioritize updating their Angular applications to the patched versions to eliminate the risk of malicious code execution via weaponized SVG animation files. Proactive security measures, including rigorous input validation, strict CSP implementation, and continuous security testing, are indispensable for building and maintaining secure web applications.