CVE-2024-10533

Executive Summary

CVE-2024-10533 is a Missing Authorization vulnerability in the WP Chat App plugin for WordPress, affecting all versions up to and including 3.6.8. The flaw resides in the ajax_install_plugin() function, which lacks a capability check, allowing authenticated attackers with Subscriber-level access or higher to install the filebird plugin without proper authorization. This unauthorized plugin installation could lead to the introduction of additional vulnerabilities or malicious functionality, potentially compromising the WordPress site's integrity.

The vulnerability has a CVSS v3.1 base score of 4.3 (Medium), with a low attack complexity and low privileges required. The EPSS score is 0.0%, indicating a low probability of exploitation in the wild at this time. No public proof-of-concept (PoC) or exploit code is available, and the vendor has not released a patch.

Supply Chain & Package Security

This vulnerability is specific to the WordPress ecosystem and the WP Chat App plugin. It does not directly affect NPM, PyPI, Go, or Ruby packages. However, the unauthorized installation of the filebird plugin could introduce supply chain risks if that plugin contains vulnerabilities or malicious code. Administrators should monitor the plugin's source and ensure only trusted plugins are installed.

CVSS Breakdown & Threat Level

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

Threat Level: Medium. While the direct impact is limited to plugin installation, the ability to install arbitrary plugins (specifically filebird) could be leveraged for further attacks, such as privilege escalation or remote code execution, depending on the installed plugin's capabilities.

Deep Dive & Mechanics

The vulnerability exists in the ajax_install_plugin() function within the WP Chat App plugin. This function is intended to handle AJAX requests for installing plugins, but it fails to perform a proper capability check (e.g., current_user_can('install_plugins')). As a result, any authenticated user with Subscriber-level access or higher can trigger the installation of the filebird plugin.

The function likely uses wp_ajax_ hooks, which are accessible to authenticated users. The missing check allows an attacker to send a crafted AJAX request to install the filebird plugin from the WordPress plugin repository. This could be exploited to introduce a plugin with known vulnerabilities or backdoors, compromising the site's security.

Root Cause: Missing capability check in ajax_install_plugin().

Attack Vector: Authenticated attacker with Subscriber-level access sends a POST request to /wp-admin/admin-ajax.php with the appropriate action and parameters.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is presumed to be in the ajax_install_plugin() function. A patched version would include a capability check.

Vulnerable Code (Conceptual):

add_action('wp_ajax_install_filebird', 'ajax_install_plugin');
function ajax_install_plugin() {
    // No capability check
    $plugin_slug = 'filebird';
    // ... installation logic
}

Patched Code (Conceptual):

add_action('wp_ajax_install_filebird', 'ajax_install_plugin');
function ajax_install_plugin() {
    if (!current_user_can('install_plugins')) {
        wp_die('Unauthorized');
    }
    $plugin_slug = 'filebird';
    // ... installation logic
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• WordPress site with WP Chat App plugin <= 3.6.8
• Authenticated user account with Subscriber role or higher
• Access to /wp-admin/admin-ajax.php

Exploitation Steps:

1. Log in as a Subscriber-level user.
2. Craft a POST request to /wp-admin/admin-ajax.php with the following parameters:
   • action: install_filebird (or similar, depending on the actual AJAX action)
   • _ajax_nonce: (if nonce is required, obtain from the page source)
3. Send the request using a tool like curl:

   curl -X POST 'http://target.com/wp-admin/admin-ajax.php' \
   -d 'action=install_filebird&_ajax_nonce=12345' \
   --cookie 'wordpress_logged_in_...=...'
   

4. Verify the filebird plugin is installed by checking the plugins page or sending a subsequent request.

Note: No public exploit code is available, so this is a conceptual demonstration.

Blue Team

Detection:

• Monitor AJAX requests to admin-ajax.php with actions related to plugin installation (e.g., install_filebird).
• Alert on any plugin installation activity from low-privileged users (Subscriber, Contributor).
• Review logs for unexpected plugin installations.

Hunting:

• Search for installed plugins that were not explicitly authorized.
• Check for the presence of the filebird plugin if it was not intentionally installed.

Indicators of Compromise (IOCs)

• File: Presence of the filebird plugin directory in /wp-content/plugins/filebird/
• Log Entry: AJAX request to /wp-admin/admin-ajax.php with action=install_filebird from a low-privileged user
• Database: Option active_plugins containing filebird/filebird.php
• Network: POST requests to /wp-admin/admin-ajax.php with suspicious parameters

Detection Engineering

YARA Rule

rule CVE_2024_10533_WP_Chat_App_Unauthorized_Plugin_Install {
    meta:
        description = "Detects exploitation attempts of CVE-2024-10533 in WP Chat App plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-10533"
    strings:
        $ajax_action = "install_filebird"
        $ajax_url = "/wp-admin/admin-ajax.php"
    condition:
        $ajax_action and $ajax_url
}

Sigma Rule

title: CVE-2024-10533 - WP Chat App Unauthorized Plugin Installation
id: 8a3f7c2e-5d1b-4a9e-8c6f-2e7b3a1d9c0f
status: experimental
description: Detects AJAX requests to install the filebird plugin without proper authorization
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: '/wp-admin/admin-ajax.php'
        cs-uri-query|contains: 'action=install_filebird'
    condition: selection
falsepositives:
    - Legitimate plugin installation by administrators
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2024-10533 - WP Chat App Unauthorized Plugin Installation Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/wp-admin/admin-ajax.php"; http_uri;
    content:"action=install_filebird"; http_client_body;
    classtype:attempted-admin;
    sid:10000001;
    rev:1;
    reference:cve,2024-10533;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the WP Chat App plugin until a patch is released.
2. Restrict user roles to prevent Subscriber-level users from accessing AJAX actions.
3. Implement a Web Application Firewall (WAF) rule to block requests containing action=install_filebird from low-privileged users.

Long-term Fix:

• The vendor should release a patched version that adds a capability check (e.g., current_user_can('install_plugins')) to the ajax_install_plugin() function.
• Alternatively, remove the AJAX handler or restrict it to administrators only.

Workaround:

• Use a security plugin to monitor and block unauthorized plugin installations.
• Regularly audit installed plugins and user permissions.

Valters IT - DevSecOps & Cyber Threat Intelligence