GHSA-h857-2g56-468g
HIGH@mattkrick/sanitize-svg vulnerable to Cross-Site Scripting (XSS)
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
@mattkrick/sanitize-svgReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
Description
Impact
The sanitize-svg package uses a deny-list-pattern to sanitize SVGs to prevent cross-site scripting (XSS). In doing so, literal <script>-tags and on-event handlers were detected:
[...]
const svgEl = div.firstElementChild!
const attributes = Array.from(svgEl.attributes).map(({ name }) => name)
const hasScriptAttr = !!attributes.find((attr) => attr.startsWith('on'))
const scripts = svgEl.getElementsByTagName('script')
return scripts.length === 0 && !hasScriptAttr ? svg : null
[...]
There are more ways to embed JavaScript in XML files.
Anchor Tag (requires user to click link):
<svg viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg">
<a href="javascript:alert(document.domain)">
<text x="50" y="50" text-anchor="middle">Lauritz</text>
</a>
</svg>
Foreign Object Tag (no user interaction required):
<svg width="500" height="500" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
<text x="20" y="35">Lauritz</text>
<foreignObject width="500" height="500">
<iframe xmlns="http://www.w3.org/1999/xhtml" src="javascript:confirm(document.domain);" width="400" height="250"/>
</foreignObject>
</svg>
As a result, downstream software that relies on sanitize-svg and expects resulting SVGs to be safe, may be vulnerable to XSS. We are aware of at least one downstream project for which this vulnerability had security implications.
Patches
This vulnerability was addressed in v0.4.0.
Workarounds
N/A
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @mattkrick/sanitize-svg | all versions | 0.4.0 |
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 @mattkrick/sanitize-svg. 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 @mattkrick/sanitize-svg to 0.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-h857-2g56-468g 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-h857-2g56-468g 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-h857-2g56-468g. 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-h857-2g56-468g in your dependencies?
O3 detects GHSA-h857-2g56-468g across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.