GHSA-fw3g-2h3j-qmm7 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in sanitize. A fix is available for sanitize — see the affected versions and patch details below.
Improper neutralization of `noscript` element content may allow XSS in Sanitize
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-fw3g-2h3j-qmm7.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-fw3g-2h3j-qmm7 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,333 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
sanitizeReal-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
Impact
Using carefully crafted input, an attacker may be able to sneak arbitrary HTML through Sanitize >= 5.0.0, < 6.0.1 when Sanitize is configured with a custom allowlist that allows noscript elements. This could result in XSS (cross-site scripting) or other undesired behavior when that HTML is rendered in a browser.
Sanitize's default configs don't allow noscript elements and are not vulnerable. This issue only affects users who are using a custom config that adds noscript to the element allowlist.
Patches
Sanitize >= 6.0.1 always removes noscript elements and their contents, even when noscript is in the allowlist.
Workarounds
Users who are unable to upgrade can prevent this issue by using one of Sanitize's default configs or by ensuring that their custom config does not include noscript in the element allowlist.
Details
The root cause of this issue is that HTML parsing rules treat the contents of a noscript element differently depending on whether scripting is enabled in the user agent. Nokogiri (the HTML parser Sanitize uses) doesn't support scripting so it follows the "scripting disabled" rules, but a web browser with scripting enabled will follow the "scripting enabled" rules. This means that Sanitize can't reliably make the contents of a noscript element safe for scripting enabled browsers. The safest thing to do is to remove the element and its contents entirely, which is now what Sanitize does in version 6.0.1 and later.
References
Credit
Thanks to David Klein from TU Braunschweig (@leeN) for reporting this issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | sanitize | ≥ 5.0.0&&< 6.0.1 | 6.0.1bundle update sanitize --conservative |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for sanitize, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update sanitize to 6.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fw3g-2h3j-qmm7 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-fw3g-2h3j-qmm7 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-fw3g-2h3j-qmm7. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Frequently Asked Questions
Is GHSA-fw3g-2h3j-qmm7 in your dependencies?
O3 Security finds GHSA-fw3g-2h3j-qmm7 across RubyGems dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.