@mattkrick/sanitize-svg vulnerable to Cross-Site Scripting (XSS)GHSA-h857-2g56-468g
HIGHFix: mattkrick/sanitize-svg@b107e45GHSA-h857-2g56-468g is a high-severity (CVSS 7.6) Cross-site Scripting (XSS) vulnerability in @mattkrick/sanitize-svg. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for @mattkrick/sanitize-svg — see the affected versions and patch details below.
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for GHSA-h857-2g56-468g.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@mattkrick/sanitize-svgnpmDescription
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 | 0.4.0npm install @mattkrick/sanitize-svg@0.4.0 |
Affected Products
sanitize-svgsanitize-svg_projectResearch 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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is GHSA-h857-2g56-468g in your dependencies?
Find it across npm, including transitive dependencies.