CVE-2026-39535: Eventbrite Events Auth Bypass Vulnerability

CVE-2026-39535 Overview

A Missing Authorization vulnerability has been identified in the fullworks Display Eventbrite Events WordPress plugin (widget-for-eventbrite-api). This security flaw allows attackers to exploit incorrectly configured access control security levels, potentially enabling unauthorized actions within WordPress installations running the affected plugin.

Critical Impact

Attackers can bypass authorization checks to access or modify plugin functionality that should be restricted to authenticated users or administrators.

Affected Products

• Display Eventbrite Events WordPress Plugin versions up to and including 6.5.6
• WordPress installations using widget-for-eventbrite-api plugin
• Sites integrating Eventbrite event display functionality via this plugin

Discovery Timeline

• 2026-04-08 - CVE CVE-2026-39535 published to NVD
• 2026-04-08 - Last updated in NVD database

Technical Details for CVE-2026-39535

Vulnerability Analysis

This vulnerability is classified as CWE-862 (Missing Authorization), a broken access control flaw where the plugin fails to properly verify user permissions before allowing access to sensitive functionality. In WordPress plugins, this typically occurs when AJAX handlers, REST API endpoints, or administrative functions lack proper capability checks using WordPress's built-in permission system.

The absence of authorization verification means that unauthenticated or low-privileged users may be able to invoke functionality intended only for administrators. This could include modifying plugin settings, accessing sensitive event data, or manipulating how Eventbrite events are displayed on the WordPress site.

Root Cause

The root cause of this vulnerability is the missing implementation of authorization checks within the Display Eventbrite Events plugin. WordPress provides functions such as current_user_can() to verify user capabilities before executing privileged operations. When these checks are absent or improperly implemented, any user—regardless of their role—may be able to trigger protected functionality.

This is a common vulnerability pattern in WordPress plugins where developers focus on functionality without implementing proper access control gates around sensitive operations.

Attack Vector

An attacker can exploit this vulnerability by directly invoking plugin endpoints or actions that lack proper authorization checks. This could be achieved through:

1. Sending crafted requests to AJAX handlers registered by the plugin
2. Accessing REST API endpoints without authentication
3. Manipulating form submissions to trigger privileged plugin functions

Since the vulnerability involves missing authorization, exploitation typically requires knowledge of the plugin's internal function names or endpoints. Attackers may discover these through code analysis of the publicly available plugin or through reconnaissance techniques.

The vulnerability does not require authentication to exploit, making it particularly dangerous for WordPress sites with the affected plugin installed.

Detection Methods for CVE-2026-39535

Indicators of Compromise

• Unexpected modifications to Eventbrite event display settings or configurations
• Unusual access patterns to WordPress AJAX endpoints associated with widget-for-eventbrite-api
• Log entries showing unauthorized users accessing plugin administrative functions
• Changes to plugin options in the wp_options database table without corresponding admin activity

Detection Strategies

• Monitor WordPress access logs for requests to admin-ajax.php with actions related to the Eventbrite widget plugin from unauthenticated sessions
• Implement Web Application Firewall (WAF) rules to detect and block requests attempting to exploit broken access control patterns
• Review plugin audit logs for any configuration changes made outside of normal administrative workflows
• Use WordPress security plugins that detect and alert on suspicious plugin behavior

Monitoring Recommendations

• Enable detailed access logging on your WordPress installation to capture all requests to plugin endpoints
• Configure alerts for any modifications to plugin settings from non-administrative IP addresses or user contexts
• Regularly audit the widget-for-eventbrite-api plugin configuration for unauthorized changes
• Monitor for any new or suspicious AJAX action hooks being triggered in your WordPress environment

How to Mitigate CVE-2026-39535

Immediate Actions Required

• Update the Display Eventbrite Events plugin to a patched version when available from the vendor
• Temporarily deactivate the widget-for-eventbrite-api plugin if critical operations can continue without it
• Implement WAF rules to restrict access to vulnerable plugin endpoints
• Review WordPress user accounts and remove any unauthorized accounts that may have been created through exploitation

Patch Information

Users should check for updates to the Display Eventbrite Events plugin through the WordPress plugin repository. Consult the Patchstack Vulnerability Report for the latest information on available patches and remediation guidance.

The vulnerability affects versions from n/a through 6.5.6 of the Display Eventbrite Events plugin. Ensure your installation is updated to a version newer than 6.5.6 once a security patch is released.

Workarounds

• Restrict access to WordPress AJAX endpoints using server-level controls such as .htaccess rules or nginx configuration
• Implement additional authentication requirements for accessing plugin functionality through a security plugin
• Consider using a virtual patching solution through a WAF service to block exploitation attempts
• Limit plugin functionality to only authenticated and trusted users until an official patch is available

# Example .htaccess rule to restrict access to admin-ajax.php
# Add this to your WordPress root .htaccess file as a temporary measure

<Files admin-ajax.php>
    <RequireAny>
        Require ip 192.168.1.0/24
        Require ip 10.0.0.0/8
    </RequireAny>
</Files>

# Note: Adjust IP ranges to match your trusted networks
# This may affect legitimate plugin functionality - test before deploying