CVE-2025-53486: WikiCategoryTagCloud: Reflected Cross-Site Scripting (XSS) via linkstyle attribute in parser function

Severity: medium (CVSS 5.4 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: 2025-07-07 · updated 2026-06-17
Weakness: CWE-79

Description

The WikiCategoryTagCloud extension is vulnerable to reflected XSS via the linkstyle attribute, which is improperly concatenated into inline HTML without escaping. An attacker can inject JavaScript event handlers such as onmouseenter using carefully crafted input via the {{#tag:tagcloud}} parser function, resulting in arbitrary JavaScript execution when a victim hovers over a link in the category cloud. The vulnerability exists because the linkstyle parameter is only passed through Sanitizer::checkCss() (which does not escape HTML) and is then directly inserted into a style attribute using string concatenation instead of Html::element or Html::openElement. This issue affects Mediawiki - WikiCategoryTagCloud extension: from 1.39.X before 1.39.13, from 1.42.X before 1.42.7, from 1.43.X before 1.43.2.

Affected products

Wikimedia Foundation Mediawiki - WikiCategoryTagCloud extension: from 1.39.x before 1.39.13; from 1.42.x before 1.42.7; from 1.43.x before 1.43.2 — fixed in 1.39.13, 1.42.7, 1.43.2

How to fix

Upgrade to a fixed version: Wikimedia Foundation Mediawiki - WikiCategoryTagCloud extension 1.39.13, 1.42.7, 1.43.2. Check the vendor advisory for mitigations.

References

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