CVE-2026-52854: Mediawiki/maps Cross-Site Scripting Vulnerability

HIGH
Advisory Identifier: GHSA-4h7g-5542-v3fc
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CVSS 8.6
CWE-80 CWE-79
Published
Advisory Summary

CVE-2026-52854 is a HIGH (CVSS 8.6) cross-site scripting vulnerability (CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)) affecting Mediawiki/maps libraries in the Packagist ecosystem. The issue involves mediawiki/maps has stored xss through the overlays parameter in the display_map parser function. Remediation is available by upgrading affected packages to version 12.1.3.

CVE-2026-52854 at a Glance

CVE Identifier CVE-2026-52854
GHSA Identifier GHSA-4h7g-5542-v3fc
Severity HIGH
CVSS v3.1 Base Score 8.6
CWE Classification CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)
Affected Product Mediawiki/maps
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 8.6

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity Low (I:L)
Availability Low (A:L)

How to Fix CVE-2026-52854

To remediate this vulnerability, upgrade all affected Mediawiki/maps dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

mediawiki/maps fixed: 12.1.3 
Upgrade mediawiki/maps to 12.1.3
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for mediawiki/maps

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-52854, inspect your project dependencies for Mediawiki/maps:

inspect dependencies for mediawiki/maps

Analyze the terminal output to locate any version of Mediawiki/maps in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 12.1.3), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS), where the product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special characters such as "<", ">", and "&" that could be interpreted as web-scripting elements when they are sent to a downstream component that processes web pages. In Mediawiki/maps, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary Stored XSS through wikitext can be performed by inserting malicious HTML into the `overlays` parameter of the `display_map` parser function when using the leaflet service. ### Details The maps extension doesn't escape overlay names before passing them to leaflet. Leaflet then inserts them as HTML: https://github.com/ProfessionalWiki/Maps/blob/ca5139fabd75f3c34f47ea3fd161306506b053bc/resources/lib/leaflet/leaflet.js#L5243 ### PoC Preview the following wikitext, using the default configuration options of the extension: ``` {{#display_map:0,0|service=leaflet|overlays=OpenTopoMap.<img src=x onerror="alert(1);">}} ``` ### Impact Stored XSS can be performed by any user with the `edit` permission.

CVE-2026-52854 Affected Mediawiki/maps Versions

1 component(s)
Fixed Versions:
12.1.3
Product / Package Ecosystem Affected Versions Fixed Version
mediawiki/maps
 Packagist
< 12.1.3
12.1.3

References

GitHub Advisory / Wiki ADVISORY
https://github.com/ProfessionalWiki/Maps/security/advisories/GHSA-4h7g-5542-v3fc
Mediawiki/maps Source Repository REPOSITORY
https://github.com/ProfessionalWiki/Maps

Frequently Asked Questions

What is CVE-2026-52854?
CVE-2026-52854 is a security vulnerability in Mediawiki/maps involving mediawiki/maps has stored XSS through the overlays parameter in the display_map parser function under CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS).
Which Mediawiki/maps versions are affected?
Affected versions include releases prior to 12.1.3 across affected packages: mediawiki/maps.
What version fixes CVE-2026-52854?
Upgrading to 12.1.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is mediawiki/maps affected?
Yes, mediawiki/maps is affected in releases prior to 12.1.3. Upgrade your dependency to 12.1.3 or later.
What is the CVSS score of CVE-2026-52854?
CVE-2026-52854 has a CVSS v3.1 base score of 8.6 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L.
What CWE is associated with CVE-2026-52854?
CVE-2026-52854 is classified under CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS) (The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special characters such as "<", ">", and "&" that could be interpreted as web-scripting elements when they are sent to a downstream component that processes web pages.).
How can I check Packagist dependencies for CVE-2026-52854?
Run the dependency tree command: 'inspect dependencies for mediawiki/maps'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-4h7g-5542-v3fc",
  "modified" : "2026-07-02T17:51:24Z",
  "published" : "2026-07-02T17:51:24Z",
  "aliases" : [ "CVE-2026-52854" ],
  "summary" : "mediawiki/maps has stored XSS through the overlays parameter in the display_map parser function",
  "details" : "### Summary\nStored XSS through wikitext can be performed by inserting malicious HTML into the `overlays` parameter of the `display_map` parser function when using the leaflet service.\n\n### Details\nThe maps extension doesn't escape overlay names before passing them to leaflet.\nLeaflet then inserts them as HTML: https://github.com/ProfessionalWiki/Maps/blob/ca5139fabd75f3c34f47ea3fd161306506b053bc/resources/lib/leaflet/leaflet.js#L5243\n\n### PoC\nPreview the following wikitext, using the default configuration options of the extension:\n```\n{{#display_map:0,0|service=leaflet|overlays=OpenTopoMap.<img src=x onerror=\"alert(1);\">}}\n```\n\n### Impact\nStored XSS can be performed by any user with the `edit` permission.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "mediawiki/maps"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "12.1.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/ProfessionalWiki/Maps/security/advisories/GHSA-4h7g-5542-v3fc"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/ProfessionalWiki/Maps"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79", "CWE-80" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-02T17:51:24Z",
    "nvd_published_at" : null
  }
}