CVE-2026-100376 TemplateSandbox can be abused for XSS by asking another user to preview a page with a certain sandbox prefix
An attacker can execute arbitrary scripts in another user's browser by tricking them into previewing a malicious page in the TemplateSandbox extension.
- 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-2026-100376?
CVE-2026-100376 is a medium-severity cross-site scripting vulnerability in Wikimedia Foundation Mediawiki - TemplateSandbox Extension, published on 25 Sep 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 (XSS or 'Cross-site Scripting') vulnerability in Wikimedia Foundation Mediawiki - TemplateSandbox Extension allows Cross-Site Scripting (XSS).
This issue affects Mediawiki - TemplateSandbox Extension: from * before 1.46.1, 1.45.5, 1.43.10.
Weakness: CWE-79
Which versions are affected by CVE-2026-100376?
How do I fix CVE-2026-100376?
No fix has been published for CVE-2026-100376 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-2026-100376 being exploited?
There is no known exploitation of CVE-2026-100376 in the wild and no public exploit code.
Sources
Also known as GHSA-8fch-w6q6-2249.