MassMessage vulnerability

An issue was discovered in the MassMessage extension in MediaWiki before 1.40.2. For a Special:MassMessage?uselang=x-xss URL, the i18n key massmessage-form-page-help allows XSS.

Published 14 Sep 2026Updated 14 Sep 20262 sources
CVSS 5.4

What happened

An issue was discovered in the MassMessage extension in MediaWiki before 1.40.2. For a Special:MassMessage?uselang=x-xss URL, the i18n key massmessage-form-page-help allows XSS.

Affected versions

MassMessage: before 1.40.2 (semver) Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

  • Apply vendor-provided updates or mitigations.
  • Review affected product exposure and access logs.

Public PoC references

No public PoC reference has passed the current publication threshold.