# CVE-2026-100240: Mediawiki TemplateSandbox Extension authorization bypass

Source: https://junglewise.ai/threats/cve-2026-100240-missing-authorization-vulnerability-in-wikimedia-foundation  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-29. Updated: 2026-09-29  
License: CC BY 4.0 with a link back

CVE-2026-100240 · Severity: info · Published 2026-09-29

The TemplateSandbox Extension for Mediawiki, used by wikis to test template edits safely, has a missing authorization check that allows users to access functionality they should not have permission to use. An attacker with wiki access could bypass access controls to perform unauthorized actions through the extension.

Vendors: [Wikimedia Foundation](https://junglewise.ai/threats/vendors/wikimedia-foundation).

## Quick answers

**Is CVE-2026-100240 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-100240 being exploited in the wild.

**How severe is CVE-2026-100240?** Informational severity, published 29 September 2026.

**Which products and versions are affected?** Wikimedia Foundation MediaWiki TemplateSandbox Extension before 1.46.1, 1.45.5, 1.43.10.

**Is there a fix for CVE-2026-100240?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-100240 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-100240?** Check whether you run Wikimedia Foundation MediaWiki TemplateSandbox Extension at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The TemplateSandbox Extension lacks proper authorization enforcement, allowing authenticated users to access features that should be restricted by access control lists. The vulnerability exists in all versions before 1.46.1, 1.45.5, and 1.43.10. An attacker requires wiki account access to exploit this authorization bypass.

## Affected products

- Wikimedia Foundation Mediawiki TemplateSandbox Extension before 1.46.1, 1.45.5, 1.43.10

## Timeline

- 2026-09-29: disclosed

## References

- [https://gerrit.wikimedia.org/r/q/Iaf9f6e2280798af5516197257ddc0264b9ad9fb7](https://gerrit.wikimedia.org/r/q/Iaf9f6e2280798af5516197257ddc0264b9ad9fb7)
- [https://phabricator.wikimedia.org/T407974](https://phabricator.wikimedia.org/T407974)

## Related threats

- [MediaWiki TemplateSandbox cross-site scripting via user namespace](https://junglewise.ai/threats/cve-2026-100376-improper-neutralization-of-input-during-web-page-generation-xss)