CVE-2024-1716

Executive Summary

CVE-2024-1716 is a security vulnerability affecting the Admin Bar Remover WordPress plugin, versions up to and including 1.0.2.2. The vulnerability is a Missing Authorization (CWE-862) flaw in the update_form() function, which allows authenticated attackers with subscriber-level access or higher to enable or disable the admin bar on the front-end of the site. This unauthorized modification of data does not require any special capabilities, making it a low-severity but exploitable issue for privilege escalation in multi-tenant WordPress environments.

Supply Chain & Package Security

This vulnerability is specific to the WordPress plugin ecosystem. The plugin is distributed via the official WordPress Plugin Directory. As of the latest analysis, no patch has been released by the vendor, and the plugin remains unpatched. Users are advised to remove or disable the plugin until a fix is available.

CVSS Breakdown & Threat Level

• CVSS Score: 4.3 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: Low (Subscriber-level)
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: None
• Integrity Impact: Low
• Availability Impact: None

The threat level is considered Medium due to the low privileges required and the potential for disruption in multi-author WordPress sites. While the impact is limited to toggling the admin bar, it can be used to degrade user experience or as a stepping stone for further attacks.

Deep Dive & Mechanics

The vulnerability resides in the update_form() function of the Admin Bar Remover plugin. This function is intended to allow administrators to configure whether the admin bar is displayed on the front-end. However, the function lacks a capability check (e.g., current_user_can('manage_options')), meaning any authenticated user, including subscribers, can call it via an AJAX request.

The plugin registers an AJAX action for both authenticated and unauthenticated users, but the unauthenticated action is properly secured. The authenticated action (wp_ajax_admin_bar_remover_update_form) does not verify the user's role, allowing subscribers to send a POST request with the admin_bar_remover_enable parameter to enable or disable the admin bar.

The core issue is the missing current_user_can() check in the update_form() function. This is a classic example of insecure direct object reference (IDOR) combined with missing authorization.

Vulnerable vs. Patched Code

Vulnerable Code (admin-bar-remover.php, version <= 1.0.2.2):

add_action('wp_ajax_admin_bar_remover_update_form', 'update_form');

function update_form() {
    // No capability check here
    if (isset($_POST['admin_bar_remover_enable'])) {
        update_option('admin_bar_remover_enable', sanitize_text_field($_POST['admin_bar_remover_enable']));
    }
    wp_die();
}

Patched Code (Hypothetical fix):

add_action('wp_ajax_admin_bar_remover_update_form', 'update_form');

function update_form() {
    // Added capability check
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized', 403);
    }
    if (isset($_POST['admin_bar_remover_enable'])) {
        update_option('admin_bar_remover_enable', sanitize_text_field($_POST['admin_bar_remover_enable']));
    }
    wp_die();
}

The patch adds a current_user_can('manage_options') check to ensure only administrators can modify the setting.

Exploitation & Lab Setup

Red Team

Prerequisites:

• A WordPress site with the Admin Bar Remover plugin installed (version <= 1.0.2.2).
• An authenticated user account with subscriber-level privileges.
• A valid WordPress nonce (if required by the plugin, though in this case the AJAX action may not require one).

Exploitation Steps:

1. Log in as a subscriber.
2. Obtain the AJAX URL: https://target.com/wp-admin/admin-ajax.php
3. Send a POST request to toggle the admin bar:

curl -X POST https://target.com/wp-admin/admin-ajax.php \
  -d "action=admin_bar_remover_update_form&admin_bar_remover_enable=0" \
  --cookie "wordpress_logged_in_<hash>=<session_cookie>"

To disable the admin bar, set admin_bar_remover_enable=0. To enable it, set admin_bar_remover_enable=1.

Expected Outcome: The admin bar is toggled for all front-end users, potentially confusing site visitors or hiding administrative controls.

Blue Team

Detection Steps:

• Monitor AJAX requests to admin-ajax.php with the action parameter set to admin_bar_remover_update_form.
• Look for requests from users with subscriber-level roles (check the wp_users table or session data).
• Alert on multiple rapid toggles of the admin bar setting.

Honeypot Strategy:

• Create a decoy WordPress site with the vulnerable plugin and monitor for exploitation attempts.
• Log all AJAX requests and correlate with user roles.

Indicators of Compromise (IOCs)

• File: /wp-content/plugins/admin-bar-remover/admin-bar-remover.php (version <= 1.0.2.2)
• Network: POST requests to /wp-admin/admin-ajax.php with action=admin_bar_remover_update_form
• Log Entry: wp_options table change for admin_bar_remover_enable option
• User Agent: Any standard HTTP client (e.g., curl, Python requests)

Detection Engineering

YARA Rule

rule Detect_Admin_Bar_Remover_Vuln {
    meta:
        description = "Detects the vulnerable Admin Bar Remover plugin version <= 1.0.2.2"
        author = "Valters IT"
        date = "2024-01-01"
        hash = "unknown"
    strings:
        $func = "update_form" ascii wide nocase
        $ajax = "wp_ajax_admin_bar_remover_update_form" ascii wide nocase
        $option = "admin_bar_remover_enable" ascii wide nocase
    condition:
        all of them
}

Sigma Rule

title: WordPress Admin Bar Remover Plugin Exploitation
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects exploitation attempts against CVE-2024-1716
author: Valters IT
date: 2024/01/01
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'action=admin_bar_remover_update_form'
    condition: selection
falsepositives:
    - Legitimate admin actions (if patched)
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"WordPress Admin Bar Remover Plugin Exploitation Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/wp-admin/admin-ajax.php"; http_uri;
    content:"action=admin_bar_remover_update_form"; http_client_body;
    classtype:attempted-recon;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Disable or remove the Admin Bar Remover plugin until a patch is released.
2. Restrict user roles to only trusted administrators.
3. Monitor logs for unauthorized AJAX requests.

Long-term Fix:

• The vendor must add a capability check (current_user_can('manage_options')) to the update_form() function.
• Alternatively, use a different plugin that properly implements authorization.

Workaround:

• Add a custom filter to block the AJAX action for non-administrators:

add_action('init', function() {
    if (defined('DOING_AJAX') && DOING_AJAX && isset($_POST['action']) && $_POST['action'] === 'admin_bar_remover_update_form') {
        if (!current_user_can('manage_options')) {
            wp_die('Unauthorized', 403);
        }
    }
});

Valters IT
Securing Digital Frontiers