GHSA-vfvf-mqq8-rwqc is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in marked. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether GHSA-vfvf-mqq8-rwqc is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Sanitization bypass using HTML Entities in marked
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, a proxy for how much of the ecosystem is exposed.
markednpmDescription
Affected versions of marked are susceptible to a cross-site scripting vulnerability in link components when sanitize:true is configured.
Proof of Concept
This flaw exists because link URIs containing HTML entities get processed in an abnormal manner. Any HTML Entities get parsed on a best-effort basis and included in the resulting link, while if that parsing fails that character is omitted.
For example:
A link URI such as
javascript֍ocument;alert(1)
Renders a valid link that when clicked will execute alert(1).
Recommendation
Update to version 0.3.6 or later.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | marked | all versions | 0.3.6 |
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 marked. 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 marked to 0.3.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-vfvf-mqq8-rwqc 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-vfvf-mqq8-rwqc 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-vfvf-mqq8-rwqc. 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-vfvf-mqq8-rwqc in your dependencies?
O3 detects GHSA-vfvf-mqq8-rwqc across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.