GHSA-43cp-6p3q-2pc4
MEDIUMHtmlSanitizer vulnerable to Cross-site Scripting in Foreign Content
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
HtmlSanitizer.NETHtmlSanitizerReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.
Description
Impact
The vulnerability occurs in configurations where foreign content is allowed, i.e. either svg or math are in the list of allowed elements.
Specifically, the requirements for the vulnerability are:
- Allowing one foreign element:
svg, ormath - Comments or one raw text element:
iframe,noembed,xmp,title,noframes,styleornoscript
Configurations that meet the above requirements plus the following are vulnerable to an additional vulnerability:
- Any HTML integration element:
title,desc,mi,mo,mn,ms,mtext,annotation-xml.
In case an application sanitizes user input with a vulnerable configuration, an attacker could bypass the sanitization and inject arbitrary HTML, including JavaScript code.
Note that in the default configuration the vulnerability is not present.
Patches
The vulnerability has been fixed in versions 8.0.723 and 8.1.722-beta (preview version).
Workarounds
Disallow foreign elements svg and math. This is the case in the default configuration, which is therefore not affected by the vulnerability.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | HtmlSanitizer | all versions | 8.0.723 |
| .NETNuGet | HtmlSanitizer | ≥ 8.1.0-beta&&< 8.1.722-beta | 8.1.722-beta |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for HtmlSanitizer. 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 HtmlSanitizer to 8.0.723 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-43cp-6p3q-2pc4 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-43cp-6p3q-2pc4 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-43cp-6p3q-2pc4. 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-43cp-6p3q-2pc4 in your dependencies?
O3 detects GHSA-43cp-6p3q-2pc4 across NuGet dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.