GHSA-pfm2-mqwj-ggm5 — mediawiki/core
MEDIUMGHSA-pfm2-mqwj-ggm5 is a medium-severity (CVSS 5.3) CWE-74 vulnerability in mediawiki/core. 1 public exploit reference exists, so weaponization risk is real. A fix is available for mediawiki/core — see the affected versions and patch details below.
MediaWiki makeCollapsible allows applying event handler to any CSS selector
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.
How urgent is this, really
GHSA-pfm2-mqwj-ggm5 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 379,145 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
mediawiki/core🐘mediawiki/core🐘mediawiki/coreReal-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
In MediaWiki before 1.34.1, users can add various Cascading Style Sheets (CSS) classes (which can affect what content is shown or hidden in the user interface) to arbitrary DOM nodes via HTML content within a MediaWiki page. This occurs because jquery.makeCollapsible allows applying an event handler to any Cascading Style Sheets (CSS) selector. There is no known way to exploit this for cross-site scripting (XSS).
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | mediawiki/core | ≥ 1.31.0&&< 1.31.7 | 1.31.7composer require mediawiki/core:^1.31.7 |
| 🐘Packagist | mediawiki/core | ≥ 1.33.0&&< 1.33.3 | 1.33.3composer require mediawiki/core:^1.33.3 |
| 🐘Packagist | mediawiki/core | ≥ 1.34.0&&< 1.34.1 | 1.34.1composer require mediawiki/core:^1.34.1 |
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 mediawiki/core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update mediawiki/core to 1.31.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-pfm2-mqwj-ggm5 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-pfm2-mqwj-ggm5 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-pfm2-mqwj-ggm5. 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-pfm2-mqwj-ggm5 in your dependencies?
O3 Security finds GHSA-pfm2-mqwj-ggm5 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.