GHSA-jq4v-f5q6-mjqq
MEDIUMGHSA-jq4v-f5q6-mjqq is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in lxml. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether GHSA-jq4v-f5q6-mjqq is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
lxml vulnerable to Cross-Site Scripting
Blast Radius
lxmlReal-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
An XSS vulnerability was discovered in the python lxml clean module versions before 4.6.3. When disabling the safe_attrs_only and forms arguments, the Cleaner class does not remove the formaction attribute allowing for JS to bypass the sanitizer. A remote attacker could exploit this flaw to run arbitrary JS code on users who interact with incorrectly sanitized HTML. This issue is patched in lxml 4.6.3.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | lxml | all versions | 4.6.3 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for lxml. 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 lxml to 4.6.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-jq4v-f5q6-mjqq 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-jq4v-f5q6-mjqq 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-jq4v-f5q6-mjqq. 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-jq4v-f5q6-mjqq in your dependencies?
O3 detects GHSA-jq4v-f5q6-mjqq across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.