CVE-2025-53093: TabberNeue MediaWiki XSS Vulnerability

CVE-2025-53093 Overview

CVE-2025-53093 is a Cross-Site Scripting (XSS) vulnerability affecting TabberNeue, a MediaWiki extension that allows wikis to create tabs. Starting in version 3.0.0 and prior to version 3.1.1, any user can insert arbitrary HTML into the DOM by inserting a payload into any allowed attribute of the <tabber> tag. This vulnerability enables attackers to execute malicious scripts in the context of other users' sessions, potentially leading to session hijacking, data theft, or defacement of wiki content.

Critical Impact

Unauthenticated attackers can inject arbitrary HTML/JavaScript through the <tabber> tag attributes, compromising the integrity and confidentiality of MediaWiki installations using the vulnerable TabberNeue extension.

Affected Products

• TabberNeue MediaWiki Extension versions 3.0.0 to < 3.1.1

Discovery Timeline

• 2025-06-27 - CVE-2025-53093 published to NVD
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2025-53093

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Cross-Site Scripting). The flaw exists in the Mustache template rendering within the TabberNeue extension, where user-controlled attribute values were rendered without proper escaping. The extension uses Mustache templates to generate HTML output for the tabber interface, and the vulnerable code used triple-brace syntax ({{{value}}}) which renders values as raw, unescaped HTML rather than the double-brace syntax ({{value}}) which automatically HTML-escapes content.

The network-accessible attack vector means any user who can edit wiki pages containing <tabber> tags can inject malicious payloads. No authentication is required in wiki configurations that allow anonymous editing, making this vulnerability particularly dangerous for public-facing MediaWiki installations.

Root Cause

The root cause lies in improper output encoding within the Mustache template files. Specifically, in includes/templates/Tabs.mustache, attribute values and tab attributes were rendered using triple braces ({{{value}}}), which bypasses Mustache's built-in HTML escaping mechanism. This allowed user-controlled data to be directly inserted into the DOM without sanitization, enabling script injection through specially crafted attribute values in the <tabber> tag.

Attack Vector

The vulnerability can be exploited by any user with edit access to wiki pages. An attacker crafts a malicious payload within the allowed attributes of a <tabber> tag. When another user views the page containing the malicious tabber content, the injected script executes in their browser context. This can be leveraged for session hijacking, credential theft, phishing attacks, or wiki content manipulation.

The patch demonstrates the fix by changing from unescaped to escaped attribute rendering:

-<div {{#array-attributes}} {{key}}="{{{value}}}"{{/array-attributes}}>{{!
+<div {{#array-attributes}} {{key}}="{{value}}"{{/array-attributes}}>{{!
 	}}<header class="tabber__header">{{!
 		}}<button class="tabber__header__prev" tabindex="-1" type="button" aria-hidden="true"></button>{{!
 		}}<nav class="tabber__tabs" role="tablist">{{!
 			}}{{#array-tabs}}{{!
-				}}<a class="tabber__tab" role="tab"{{#array-tab-attributes}} {{key}}="{{{value}}}"{{/array-tab-attributes}}>{{{label}}}</a>{{!
+				}}<a class="tabber__tab" role="tab"{{#array-tab-attributes}} {{key}}="{{value}}"{{/array-tab-attributes}}>{{{label}}}</a>{{!
 			}}{{/array-tabs}}{{!
 		}}</nav>{{!
 		}}<button class="tabber__header__next" tabindex="-1" type="button" aria-hidden="true"></button>{{!

Source: GitHub Commit Update

Detection Methods for CVE-2025-53093

Indicators of Compromise

• Unexpected JavaScript execution when viewing wiki pages containing <tabber> elements
• Anomalous HTML content within tabber tag attributes in wiki source code
• User reports of suspicious behavior, pop-ups, or redirects when viewing tabbed content

Detection Strategies

• Review recent wiki page edits for suspicious payloads in <tabber> tag attributes
• Implement Content Security Policy (CSP) headers to detect and block inline script execution
• Monitor web application firewall (WAF) logs for XSS attack patterns targeting tabber functionality
• Audit wiki revision history for pages containing <tabber> tags

Monitoring Recommendations

• Enable detailed logging on the MediaWiki server to track page rendering errors
• Configure browser-based XSS detection alerts through security monitoring tools
• Set up alerts for CSP violation reports indicating potential XSS attempts

How to Mitigate CVE-2025-53093

Immediate Actions Required

• Upgrade TabberNeue extension to version 3.1.1 or later immediately
• Audit all wiki pages containing <tabber> tags for malicious content
• Review recent page edits for potential exploitation attempts
• Implement Content Security Policy headers to mitigate XSS impact

Patch Information

The vulnerability has been patched in TabberNeue version 3.1.1. The fix modifies the Mustache template rendering to properly escape attribute values, preventing HTML injection. The security patches are available through the GitHub Security Advisory and related commits.

The patched code includes a rewritten parser tag implementation with improved security:

<?php
declare( strict_types=1 );

namespace MediaWiki\Extension\TabberNeue\Components;

/**
 * @internal
 */
interface TabberComponent {
	public function getTemplateData(): array;
}

Source: GitHub Commit Changes

Workarounds

• Temporarily disable the TabberNeue extension until upgrade is possible
• Restrict wiki edit permissions to trusted users only
• Implement strict Content Security Policy headers to block inline script execution
• Use a Web Application Firewall (WAF) with XSS filtering rules

# MediaWiki LocalSettings.php - Disable TabberNeue temporarily
# Comment out or remove the TabberNeue extension loading line
# wfLoadExtension( 'TabberNeue' );

# Implement Content Security Policy header in Apache/Nginx
# Apache (.htaccess or httpd.conf)
Header set Content-Security-Policy "default-src 'self'; script-src 'self'"

# Nginx (nginx.conf or site config)
add_header Content-Security-Policy "default-src 'self'; script-src 'self'";