CVE-2026-52854 mediawiki/maps: Stored XSS through the overlays parameter in the display_map parser function
A stored XSS vulnerability in the MediaWiki Maps extension allows attackers to execute scripts in viewers' browsers via the overlays parameter.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-52854?
CVE-2026-52854 is a high-severity cross-site scripting vulnerability in ProfessionalWiki Maps, published on 18 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-52854?
2 open source packages ship an affected version, including mediawiki/maps.
| Package | Affected | Fixed in |
|---|---|---|
mediawiki/maps Packagist | All versions | 12.1.3 |
mediawiki/maps Packagist | All versions | 12.1.3 |
How do I fix CVE-2026-52854?
Upgrade mediawiki/maps to 12.1.3 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-52854 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-52854 exists.
Sources
Also known as GHSA-4h7g-5542-v3fc, UBUNTU-CVE-2026-52854.