CVE-2026-39840 CSS injection in multiple Cargo display formats
Attackers can inject malicious CSS into MediaWiki pages via the Cargo extension, potentially leading to script execution or session hijacking.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-39840?
CVE-2026-39840 is a medium-severity cross-site scripting vulnerability in Wikimedia Foundation Mediawiki - Cargo Extension, published on 7 Apr 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
Improper neutralization of input during web page generation ('cross-site scripting') vulnerability in Wikimedia Foundation Mediawiki - Cargo Extension allows XSS Targeting Non-Script Elements.This issue affects Mediawiki - Cargo Extension: before 3.8.7.
Weakness: CWE-79
Which versions are affected by CVE-2026-39840?
It affects 1 product.
Products include Mediawiki Cargo.
How do I fix CVE-2026-39840?
No fix has been published for CVE-2026-39840 yet. Limit exposure of the affected software until one is available.
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-2026-39840 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39840 exists.
Other vulnerabilities in Wikimedia Foundation Mediawiki - Cargo Extension
- CVE-2024-47849 Backticks can allow the usage of not-allowed SQL functions
- CVE-2026-14363 Cargo Extension: SQLi in Special:Drilldown
- CVE-2026-58519 Stored XSS through Cargo's map format
- CVE-2026-58521 SQLi in Cargo extension via year range filter
- CVE-2024-47846 Special:DeleteCargoTable and Special:SwitchCargoTable have no CSRF protection
Sources
Also known as GHSA-8m8x-w498-p4wx.