GHSA-mcvf-2q2m-x72m
MEDIUMGHSA-mcvf-2q2m-x72m is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in rails-html-sanitizer. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether GHSA-mcvf-2q2m-x72m is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Improper neutralization of data URIs may allow XSS in rails-html-sanitizer
Real-World Exposure
rails-html-sanitizerReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
Summary
rails-html-sanitizer >= 1.0.3, < 1.4.4 is vulnerable to cross-site scripting via data URIs when used in combination with Loofah >= 2.1.0.
Mitigation
Upgrade to rails-html-sanitizer >= 1.4.4.
Severity
The maintainers have evaluated this as Medium Severity 6.1.
References
- CWE - CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (4.9)
- SVG MIME Type (image/svg+xml) is misleading to developers · Issue #266 · w3c/svgwg
- https://github.com/rails/rails-html-sanitizer/issues/135
- https://hackerone.com/reports/1694173
Credit
This vulnerability was independently reported by Maciej Piechota (@haqpl) and Mrinmoy Das (@goromlagche).
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | rails-html-sanitizer | ≥ 1.0.3&&< 1.4.4 | 1.4.4 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for rails-html-sanitizer. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update rails-html-sanitizer to 1.4.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-mcvf-2q2m-x72m is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-mcvf-2q2m-x72m is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-mcvf-2q2m-x72m. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-mcvf-2q2m-x72m in your dependencies?
O3 detects GHSA-mcvf-2q2m-x72m across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.