GHSA-qvc2-mg72-jjhx — justhtml
GHSA-qvc2-mg72-jjhx is a Cross-site Scripting (XSS) vulnerability in justhtml. A fix is available for justhtml — see the affected versions and patch details below.
JustHTML Affected by Mutation XSS via Literal Text Serialization in Raw Text Elements (style/script)
Exploitation Status
No confirmed exploitation observed yet
- 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-qvc2-mg72-jjhx.
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
justhtmlReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
Sanitized DOM trees can be unsafe to serialize when a custom policy allows raw-text elements such as <style> or <script>.
The issue affects DOM trees that are constructed or modified programmatically and then passed through sanitize_dom() with a policy that keeps these elements. Text nodes inside <style> and <script> are serialized literally, so attacker-controlled text containing the matching closing tag sequence can break out of the raw-text context and inject HTML into the serialized output.
The default sanitization policy is not affected because it drops the contents of style and script.
Details
The root cause is in HTML serialization of raw-text elements. In serialize.py, text children of script and style are emitted verbatim:
_LITERAL_TEXT_SERIALIZATION_ELEMENTS = frozenset({"script", "style"})
def _serialize_text_for_parent(text: str | None, parent_name: str | None) -> str:
if not text:
return ""
if parent_name in _LITERAL_TEXT_SERIALIZATION_ELEMENTS:
return text
return _escape_text(text)
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | justhtml | all versions | 1.12.0pip install --upgrade 'justhtml==1.12.0' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for justhtml, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update justhtml to 1.12.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-qvc2-mg72-jjhx 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-qvc2-mg72-jjhx can be triaged on real exposure rather than presence alone.
Tailored to GHSA-qvc2-mg72-jjhx. 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-qvc2-mg72-jjhx in your dependencies?
O3 Security finds GHSA-qvc2-mg72-jjhx across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.