---
id: "CVE-2026-126564"
page: "https://infrastack.ai/live/CVE-2026-126564"
kind: "vulnerability"
aliases: ["CVE-2026-126564"]
title: "Semantic MediaWiki: stored script injection through property labels in Special:Browse"
severity: "medium"
cvss: 5.4
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["mediawiki", "package", "self-hosted", "semantic-mediawiki"]
not_affected_if: ["extension-not-installed", "fixed-version"]
published_at: "2026-11-11T03:16:50+00:00"
first_seen_at: "2026-11-11T03:25:00+00:00"
updated_at: "2026-11-11T03:26:29+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-126564", "first_seen_at": "2026-11-11T03:25:00+00:00"}]
exploit_sources: []
---

# Semantic MediaWiki: stored script injection through property labels in Special:Browse

Link for people: https://infrastack.ai/live/CVE-2026-126564 (this .md is for agents)

Semantic MediaWiki versions from 2.5.0 up to but not including 7.4.1 fail to escape property label text when it is rendered on Special:Browse and the smwbrowse API. A user with page-edit rights can save a label containing an image onerror payload that runs in the browser of anyone who views it, including administrators.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed Semantic MediaWiki version in Special:Version or the extension's `composer.lock` / `extension.json`, and compare against `7.4.1`.
- Review Semantic MediaWiki preferred property labels for HTML such as `<img onerror=...>` on the wiki.

## Fix

- Semantic MediaWiki: upgrade to `7.4.1` or later.

## Timeline

- 2026-11-11T03:25:00+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-126564

## Documents

- [advisory] Vendor advisory: github.com https://github.com/SemanticMediaWiki/SemanticMediaWiki/security/advisories/GHSA-mc5x-2j7v-x8hp
- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/semantic-mediawiki-2.5.0-before-7.4.1-stored-xss-via-special-browse-factbox-title
- [fix] Patch: github.com https://github.com/SemanticMediaWiki/SemanticMediaWiki/commit/c9bf9f25549bb2f5eab916339b267a1732002c4c
- [fix] Release notes: github.com https://github.com/SemanticMediaWiki/SemanticMediaWiki/releases/tag/7.4.1

## From the sources

Semantic MediaWiki 2.5.0 before 7.4.1 contains a stored cross-site scripting vulnerability in ValueFormatter::getFormattedSubject() that renders property label segments after a literal &nbsp; as unescaped markup. Users with page-edit rights can set a preferred property label containing an img onerror payload that executes when anyone, including administrators, views Special:Browse or the smwbrowse API.

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_