CVE-2026-39936
Cross-Site Scripting in Mediawiki Score Extension Enables Code Injection
Publication date: 2026-04-07
Last updated on: 2026-04-08
Assigner: wikimedia-foundation
Description
Description
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| the_wikimedia_foundation | mediawiki_score_extension | * |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-79 | The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability is a Cross-Site Scripting (XSS) issue in the Wikimedia Foundation Mediawiki - Score Extension. It occurs because the extension improperly neutralizes input during web page generation, allowing malicious scripts to be injected and executed in the context of a user's browser.
How can this vulnerability impact me? :
The impact of this vulnerability includes the potential for attackers to execute arbitrary scripts in users' browsers. This can lead to theft of sensitive information, session hijacking, defacement of web content, or redirection to malicious sites.
How can this vulnerability be detected on my network or system? Can you suggest some commands?
This vulnerability can be detected by inspecting the HTML output of pages using the MediaWiki Score extension for the presence of non-reserved data attributes such as `data-midi` and `data-source` containing unsafe URLs like those starting with `javascript:`. Additionally, checking for stored XSS payloads in pages embedding SVG images generated by Scribunto Lua modules can help identify exploitation.
Since the issue involves unsafe href attributes derived from these data attributes, you can use web application scanning tools or manual inspection to look for links with suspicious JavaScript URLs.
Suggested commands or approaches include:
- Use browser developer tools or curl to fetch pages that use the Score extension and grep for `data-midi` or `data-source` attributes containing `javascript:` URLs.
- Example command to fetch and search a page (replace URL accordingly):
- curl -s https://your-mediawiki-site/wiki/Page_with_Score_Extension | grep -E 'data-midi|data-source'
- Use automated web vulnerability scanners that detect stored XSS vulnerabilities by crawling and interacting with pages.
What immediate steps should I take to mitigate this vulnerability?
Immediate mitigation steps include applying the official patch that changes the Score extension to use reserved data attributes prefixed with `data-mw-` instead of non-reserved attributes. This patch prevents unsafe URL injection and stored XSS.
After deploying the patch, it is critical to purge affected pages to clear cached parser output and remove unsafe attributes from the rendered HTML.
Additional recommendations include:
- Deploy the patch merged across supported branches (master, REL1_43, REL1_44, REL1_45).
- Purge all pages using the Score extension to update caches and remove unsafe data attributes.
- Consider implementing a Content Security Policy (CSP) to mitigate the impact of any future XSS vulnerabilities.