GHSA-j92c-7v7g-gj3f
HtmlSanitizer has a bypass via template tag
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
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 | 9.0.892 |
| .NETNuGet | HtmlSanitizer | ≥ 9.1.878-beta&&< 9.1.893-beta | 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. 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 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 pinpoints whether GHSA-j92c-7v7g-gj3f 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-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 detects GHSA-j92c-7v7g-gj3f across NuGet dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.