CVE-2026-58034: Stored XSS through a system message when blocking a temporary account that's related to other temporary accounts

Severity: medium (CVSS 4.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-01 · updated 2026-10-25
Weakness: CWE-79

Description

Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting') vulnerability in Wikimedia Foundation CheckUser. This vulnerability is associated with program files modules/ext.CheckUser.TempAccounts/components/blockConnectedTempAccountsField.Vue. This issue affects CheckUser: from 1.46.0-rc.0 before 1.46.0.

Affected products

Wikimedia Foundation MediaWiki: 1.46.0-rc0

References

https://phabricator.wikimedia.org/T428820

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