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Stored XSS through short descriptions

High
alistair3149 published GHSA-prmv-7r8c-794g Jul 3, 2025

Package

Citizen (MediaWiki)

Affected versions

>= 65a7ffd927467c8c3557146d1ac6de62b0369b6c

Patched versions

>= c85a40bddc8651fff66df83a72debddcb34f0521

Description

Summary

Short descriptions set via the ShortDescription extension are inserted as raw HTML by the Citizen skin, allowing any user to insert arbitrary HTML into the DOM by editing a page.

Details

The shortdesc property, which contains unsanitized user input, is retrieved from the OutputPage and returned as the tagline:

mediawiki-skins-Citizen/includes/Components/CitizenComponentPageHeading.php

Lines 249 to 251 in 0d8a440

$shortdesc = $this->out->getProperty( 'shortdesc' );
if ( $shortdesc ) {
$tagline = $shortdesc;

The tagline is then provided to the template data:

mediawiki-skins-Citizen/includes/Components/CitizenComponentPageHeading.php

Lines 270 to 275 in 0d8a440

public function getTemplateData(): array {
return [
'html-tagline' => $this->getTagline(),
'html-title-heading' => $this->getPageHeading()
];
}

The template then inserts the tagline into raw HTML without doing any escaping:

mediawiki-skins-Citizen/templates/PageHeading.mustache

Line 12 in 0d8a440

<div id="siteSub">{{{html-tagline}}}</div>

PoC

  1. Enable Citizen and ShortDescription
  2. Add {{SHORTDESC:&lt;img src="" onerror="alert('citizen shortdescription xss')"&gt;}} to a page
  3. Visit the page
    image
    image

Impact

Arbitrary HTML can be inserted into the DOM by any user, allowing for JavaScript to be executed.

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
Low
Availability
Low

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L

CVE ID

CVE-2025-53370

Weaknesses

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Learn more on MITRE.

Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)

The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special characters such as <, >, and & that could be interpreted as web-scripting elements when they are sent to a downstream component that processes web pages. Learn more on MITRE.

Credits