svg-security web-vulnerabilities developer-tools content-sanitization

The woes of sanitizing SVGs

muffin.ink

April 27, 2026

13 min read

🔥🔥🔥🔥🔥

61/100

Summary

Scratch has a history of SVG-related vulnerabilities due to the parsing of user-generated content into an <svg> element, which is appended to the main document. This operation poses inherent security risks, leading Scratch to implement increasingly complex sanitization methods.

Key Takeaways

Scratch has a history of SVG-related vulnerabilities due to parsing user-generated content into an <svg> element, which poses security risks.
In 2019, Scratch addressed an XSS vulnerability caused by <script> tags in SVGs by using a regular expression to remove them.
Subsequent vulnerabilities in 2020 and 2022 revealed that previous fixes were inadequate, allowing XSS attacks and HTTP leaks through various methods.
As of 2023, Scratch continues to face challenges with SVG sanitization, indicating that its current approach may be insufficient for ensuring security.

Read original article

View story →

Coverage & discussions

Hacker News · muffin.ink

The woes of sanitizing SVGs ↗

Community discussions

Hacker News discussion ↗

Historical count: 5 · 5 saved in sample · Historical sample

Analysis ready

Community Sentiment

Mixed

Positives

The article highlights the importance of Content Security Policy (CSP) as a credible solution for addressing HTTP leak problems, which is crucial for enhancing web security.
The suggestion of a sandbox attribute for inline SVG tags could significantly improve security by restricting dynamic content, though it may face browser support challenges.

Concerns

The lack of an industry standard for SVG sanitization hampers usability, as users cannot guarantee compatibility across different tools and browsers.
Relying on regular expressions for sanitizing SVGs is problematic, as it can lead to security vulnerabilities and does not address the complexity of SVG content.