GHSA-fw3g-2h3j-qmm7
MEDIUMImproper neutralization of `noscript` element content may allow XSS in Sanitize
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.
Blast Radius
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 | 6.0.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for sanitize. 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 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 pinpoints whether GHSA-fw3g-2h3j-qmm7 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-fw3g-2h3j-qmm7. 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-fw3g-2h3j-qmm7 in your dependencies?
O3 detects GHSA-fw3g-2h3j-qmm7 across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.