CVE-2024-0828

Executive Summary

CVE-2024-0828 is a missing authorization vulnerability in the Play.ht – Make Your Blog Posts Accessible With Text to Speech Audio WordPress plugin, affecting all versions up to and including 3.6.4. The plugin fails to perform proper capability checks on several AJAX actions, allowing authenticated attackers with subscriber-level access or higher to delete, retrieve, or modify post metadata, retrieve contents of protected posts, modify conversion data, and delete article audio. This vulnerability is classified as a Broken Access Control issue (CWE-862) with a CVSS v3.1 base score of 5.4 (Medium). The EPSS score is 0.0%, indicating low exploitation likelihood in the wild, but the impact on confidentiality and integrity is significant for WordPress sites using this plugin.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. No NPM, PyPI, Go, or Ruby packages are involved. The plugin is installed directly on WordPress sites, and the risk is limited to the WordPress ecosystem.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – The vulnerability is exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): Low (L) – Attacker needs subscriber-level authentication.
• User Interaction (UI): None (N) – No user action is required.
• Scope (S): Unchanged (U) – The vulnerable component and impacted component are the same.
• Confidentiality (C): Low (L) – Limited disclosure of post metadata and protected post contents.
• Integrity (I): Low (L) – Limited modification of post metadata and conversion data.
• Availability (A): None (N) – No impact on availability.

Threat Level: Medium. The vulnerability requires authentication but allows low-privileged users to access and modify sensitive data.

Deep Dive & Mechanics

The Play.ht plugin registers several AJAX actions for handling text-to-speech conversion, post metadata management, and audio file operations. These actions are defined in the plugin's main PHP file (typically play-ht.php or similar). The vulnerability arises because the plugin does not enforce capability checks (e.g., current_user_can('edit_posts')) before executing these actions. As a result, any authenticated user, including subscribers, can call these endpoints.

Key affected functions include:

• play_ht_delete_post_meta – Deletes post metadata.
• play_ht_get_post_meta – Retrieves post metadata.
• play_ht_update_post_meta – Updates post metadata.
• play_ht_get_protected_post_content – Retrieves content of password-protected or private posts.
• play_ht_delete_article_audio – Deletes generated audio files.
• play_ht_modify_conversion_data – Modifies conversion settings.

The missing capability check allows an attacker to enumerate and manipulate post data, potentially exposing sensitive information or disrupting the site's audio functionality.

Vulnerable vs. Patched Code

Vulnerable Code (<= 3.6.4):

add_action('wp_ajax_play_ht_delete_post_meta', 'play_ht_delete_post_meta_callback');
function play_ht_delete_post_meta_callback() {
    // No capability check
    $post_id = intval($_POST['post_id']);
    delete_post_meta($post_id, 'play_ht_audio_url');
    wp_die();
}

Patched Code (Hypothetical):

add_action('wp_ajax_play_ht_delete_post_meta', 'play_ht_delete_post_meta_callback');
function play_ht_delete_post_meta_callback() {
    if (!current_user_can('edit_post', intval($_POST['post_id']))) {
        wp_die('Unauthorized', 403);
    }
    $post_id = intval($_POST['post_id']);
    delete_post_meta($post_id, 'play_ht_audio_url');
    wp_die();
}

The patch adds a capability check using current_user_can('edit_post', $post_id) to ensure only users with edit permissions on the specific post can perform the action.

Exploitation & Lab Setup

Red Team

1. Prerequisites: Obtain subscriber-level credentials on a WordPress site with the Play.ht plugin installed (<= 3.6.4).
2. Exploit Steps:
   • Log in as a subscriber.
   • Use browser developer tools or a tool like Burp Suite to send AJAX requests to the vulnerable endpoints.
   • Example request to retrieve post metadata:

     POST /wp-admin/admin-ajax.php HTTP/1.1
     Content-Type: application/x-www-form-urlencoded
     Cookie: [subscriber session cookie]
     
     action=play_ht_get_post_meta&post_id=1
     

   • Example request to delete article audio:

     POST /wp-admin/admin-ajax.php HTTP/1.1
     Content-Type: application/x-www-form-urlencoded
     Cookie: [subscriber session cookie]
     
     action=play_ht_delete_article_audio&post_id=1
     

3. Automation: Use a Python script to iterate over post IDs and extract metadata or delete audio files.

Blue Team

1. Detection: Monitor AJAX requests to admin-ajax.php with actions starting with play_ht_ from low-privileged users (subscriber, contributor).
2. Honeypot: Create a fake subscriber account and monitor its activity for unusual AJAX calls.
3. Mitigation: Apply the principle of least privilege by restricting subscriber capabilities. Use a Web Application Firewall (WAF) to block suspicious AJAX requests.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Repeated POST requests to /wp-admin/admin-ajax.php with action=play_ht_* parameters from a single IP.
  • Unusual patterns of post metadata retrieval or deletion.
• File IOCs:
  • Missing audio files in the WordPress uploads directory (/wp-content/uploads/play-ht-audio/).
  • Modified postmeta table entries for play_ht_audio_url.
• Log IOCs:
  • WordPress debug log entries showing failed capability checks (if patched).
  • Web server access logs showing multiple admin-ajax.php requests with play_ht_ actions.

Detection Engineering

YARA Rule

rule Detect_PlayHT_Exploit {
    meta:
        description = "Detects exploitation attempts of CVE-2024-0828 in Play.ht plugin"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2024-0828"
    strings:
        $ajax_action = /action=play_ht_(delete|get|update)_post_meta|play_ht_get_protected_post_content|play_ht_delete_article_audio|play_ht_modify_conversion_data/
        $wp_ajax = "wp_ajax_play_ht_"
    condition:
        $ajax_action or $wp_ajax
}

Sigma Rule

title: CVE-2024-0828 Play.ht Plugin Exploitation
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects exploitation attempts of CVE-2024-0828 in Play.ht WordPress plugin
author: Valters IT
date: 2024/01/01
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'admin-ajax.php'
        cs-uri-query|contains|all:
            - 'action=play_ht_'
    condition: selection
falsepositives:
    - Legitimate plugin usage by authorized users
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-0828 Play.ht Plugin Exploitation Attempt"; flow:to_server,established; content:"POST"; http_method; content:"admin-ajax.php"; http_uri; content:"action=play_ht_"; http_client_body; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Actions:
   • Update the Play.ht plugin to the latest version if a patch is released.
   • If no patch is available, disable the plugin until a fix is provided.
   • Restrict subscriber capabilities using a plugin like "User Role Editor" to prevent AJAX access.
2. Long-term Measures:
   • Implement a Web Application Firewall (WAF) with rules to block unauthorized AJAX requests.
   • Regularly audit WordPress plugins for missing capability checks.
   • Monitor WordPress logs for suspicious activity.
3. Workaround:
   • Add a custom capability check via a mu-plugin:

     add_action('init', function() {
         $actions = ['play_ht_delete_post_meta', 'play_ht_get_post_meta', 'play_ht_update_post_meta', 'play_ht_get_protected_post_content', 'play_ht_delete_article_audio', 'play_ht_modify_conversion_data'];
         foreach ($actions as $action) {
             add_action("wp_ajax_$action", function() use ($action) {
                 if (!current_user_can('edit_posts')) {
                     wp_die('Unauthorized', 403);
                 }
             }, 0);
         }
     });
     

Valters IT
Securing Digital Frontiers