GHSA-j92c-7v7g-gj3f — HtmlSanitizer
Fix: mganss/HtmlSanitizer@0ac53dcGHSA-j92c-7v7g-gj3f is a CWE-116 vulnerability in HtmlSanitizer. A fix is available for HtmlSanitizer — see the affected versions and patch details below.
HtmlSanitizer has a bypass via template tag
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-j92c-7v7g-gj3f.
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.
Real-World Exposure
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
If the template tag is allowed, its contents are not sanitized. The template tag is a special tag that does not usually render its contents, unless the shadowrootmode attribute is set to open or closed.
The lack of sanitization of the template tag brings up two bypasses:
- it is still possible to forcibly render the contents of a
<template>tag through mutation XSS. The DOM parsers in browsers such as Chromium have a node depth limit of 512 and tags which are beyond that depth are flattened. This in turn allows elements within<template>(which are not sanitized) to be effectively 'popped out'. An example would look like this:<div>[...]<template><script>alert('xss')</script>where[...]denotes at least another 509 opening<div>tags. - If in addition to the template tag, the
shadowrootmodeattribute is allowed throughsanitizer.AllowedAttributes.Add("shadowrootmode");, the simple payload of<div><template shadowrootmode="open"><script>alert('xss')</script>would bypass the sanitizer. This is because such usage of<template>attaches a shadow root to its parent:<div>, and its contents will be rendered.
Note that the default configuration is not affected because the template tag is disallowed by default.
Patches
The problem has been patched in versions 9.0.892 and 9.1.893-beta.
Workarounds
Disallow the template tag. It is disallowed by default.
Resources
https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements/template
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | HtmlSanitizer | all versions | 9.0.892dotnet add package HtmlSanitizer --version 9.0.892 |
| .NETNuGet | HtmlSanitizer | ≥ 9.1.878-beta&&< 9.1.893-beta | 9.1.893-betadotnet add package HtmlSanitizer --version 9.1.893-beta |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for HtmlSanitizer, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update HtmlSanitizer to 9.0.892 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-j92c-7v7g-gj3f 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-j92c-7v7g-gj3f can be triaged on real exposure rather than presence alone.
Tailored to GHSA-j92c-7v7g-gj3f. 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-j92c-7v7g-gj3f in your dependencies?
O3 Security finds GHSA-j92c-7v7g-gj3f across NuGet dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.