CVE-2021-30458
MEDIUMCVE-2021-30458 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in wikimedia/parsoid. O3 Security confirms whether CVE-2021-30458 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Wikimedia Parsoid vulnerable to Cross-site Scripting (XSS)
Blast Radius
wikimedia/parsoid🐘wikimedia/parsoidReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
An issue was discovered in Wikimedia Parsoid before 0.11.1 and 0.12.x before 0.12.2. An attacker can send crafted wikitext that Utils/WTUtils.php will transform by using a <meta> tag, bypassing sanitization steps, and potentially allowing for XSS.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | wikimedia/parsoid | ≥ 0.12&&< 0.12.2 | 0.12.2 |
| 🐘Packagist | wikimedia/parsoid | all versions | 0.11.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for wikimedia/parsoid. 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 wikimedia/parsoid to 0.12.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-30458 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 CVE-2021-30458 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 CVE-2021-30458. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2021-30458 in your dependencies?
O3 detects CVE-2021-30458 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.