Medium severity · published Jul 1, 2026
CVE-2026-58034
Stored XSS through a system message when blocking a temporary account that's related to other temporary accounts
4.8
CVSS
0.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
High
User interaction
Required
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 21% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CH
CheckUser · Wikimedia Foundation
1.46.0-rc.0 before 1.46.0 · source: vendor
ME
Mediawiki · Mediawiki
1.46.0 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-58034
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-58034
Permissions Required
https://phabricator.wikimedia.org/T428820
More from CheckUser
8.8
CVE-2025-67478
Wrong E-Mail address composition for usernames with a comma and Umlauts in it like "Döe, Jähn"
7.5
CVE-2026-34090
Suggested investigations: Handle suppressed usernames
6.1
CVE-2025-61651
i18n XSS through Special:CheckUser CheckUser helper
6.1
CVE-2025-61648
Stored XSS through system messages in CheckUser
4.3
CVE-2025-61658
Special:GlobalContributions shows edits on wikis the viewer doesn't have access to