GHSA-g955-vw6w-v6pp
MEDIUMCitizen vulnerable to stored XSS in sticky header button messages
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
starcitizentools/citizen-skinReal-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
Summary
The JS implementation for copying button labels to the sticky header in the Citizen skin unescapes HTML characters, allowing for stored XSS through system messages.
Details
In the copyButtonAttributes function in stickyHeader.js, when copying the button labels, the innerHTML of the new element is set to the textContent of the old element:
https://github.com/StarCitizenTools/mediawiki-skins-Citizen/blob/f4cbcecf5aca0ae69966b23d4983f9cb5033f319/resources/skins.citizen.scripts/stickyHeader.js#L29-L41
This unescapes any escaped HTML characters and causes the contents of the system messages to be interpreted as HTML.
PoC
- Edit any of the affected messages (
citizen-share,citizen-view-history,citizen-view-edit,nstab-talk) to the following payload:<img src="" onerror="alert('Sticky Header Button XSS')">. - Visit any mainpage article in the wiki using the Citizen skin.
Impact
This impacts wikis where a group has the editinterface but not the editsitejs user right. By default, this is the case for the sysop group.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | starcitizentools/citizen-skin | ≥ 3.3.0&&< 3.9.0 | 3.9.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for starcitizentools/citizen-skin. 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 starcitizentools/citizen-skin to 3.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-g955-vw6w-v6pp 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-g955-vw6w-v6pp 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-g955-vw6w-v6pp. 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-g955-vw6w-v6pp in your dependencies?
O3 detects GHSA-g955-vw6w-v6pp across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.