GHSA-x52f-h5g4-8qv5
MEDIUMMarp Core allows XSS by improper neutralization of HTML sanitization
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
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
@marp-team/marp-corenpmDescription
Marp Core (@marp-team/marp-core) from v3.0.2 to v3.9.0 and v4.0.0, are vulnerable to cross-site scripting (XSS) due to improper neutralization of HTML sanitization.
Impact
Marp Core includes an HTML sanitizer with allowlist support. In the affected versions, the built-in allowlist is enabled by default. When the allowlist is active, if insufficient HTML comments are included, the sanitizer may fail to properly sanitize HTML content and lead cross-site scripting (XSS).
Patches
Marp Core v3.9.1 and v4.0.1 have been patched to fix that.
Workarounds
If you are unable to update the package immediately, disable all HTML tags by setting html: false option in the Marp class constructor.
const marp = new Marp({ html: false })
References
- CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
- https://github.com/marp-team/marp-core/pull/282
- https://github.com/marp-team/marp-core/commit/61a1def244d1b6faa8e2c0be97ec0b68cab3ab49
Credits
Thanks to @Ry0taK for finding out this vulnerability.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @marp-team/marp-core | ≥ 3.0.2&&< 3.9.1 | 3.9.1 |
| 📦npm | @marp-team/marp-core | ≥ 4.0.0&&< 4.0.1 | 4.0.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @marp-team/marp-core. 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 @marp-team/marp-core to 3.9.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-x52f-h5g4-8qv5 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-x52f-h5g4-8qv5 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-x52f-h5g4-8qv5. 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-x52f-h5g4-8qv5 in your dependencies?
O3 detects GHSA-x52f-h5g4-8qv5 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.