CVE-2026-52854 is a high-severity (CVSS 8.6) Cross-site Scripting (XSS) vulnerability in mediawiki/maps. A fix is available for mediawiki/maps — see the affected versions and patch details below.
mediawiki/maps: Stored XSS through the overlays parameter in the display_map parser function
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-52854.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-52854 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 394,803 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
mediawiki/mapsReal-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
Maps is a MediaWiki extension that enables visualization of geographic data through dynamic embedded maps. Prior to version 12.1.3, the display_map parser function in the Leaflet service accepts attacker-controlled HTML in the overlays parameter, and resources/leaflet/jquery.leaflet.js uses the overlay name as a Leaflet layer-control label without escaping it. A wiki user with the edit permission can store malicious wikitext that causes script execution when another user previews or views the affected map. The script executes in the viewing user's browser session and can access data or perform actions available to that user. This issue is fixed in version 12.1.3.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | mediawiki/maps | all versions | 12.1.3composer require mediawiki/maps:^12.1.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mediawiki/maps, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update mediawiki/maps to 12.1.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-52854 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.
Frequently Asked Questions
Is CVE-2026-52854 in your dependencies?
Find it across Packagist, including transitive dependencies.