Mercado Pago payments for WooCommerce < 8.7.12 - Missing Authorization to Unauthenticated PIX Payment QR Code Image Disclosure

Description

The Mercado Pago payments for WooCommerce plugin for WordPress is vulnerable to unauthorized access of data due to a missing capability check on the 'mp_pix_image' WooCommerce API endpoint in all versions up to, and including, 8.7.11. This makes it possible for unauthenticated attackers to retrieve PIX payment QR code images for arbitrary orders. PIX QR codes contain sensitive merchant information including PIX keys (which may be CPF/CNPJ personal identifiers), transaction amounts, merchant name and city, and MercadoPago transaction references.