The WebToffee WooCommerce PDF Invoices, Packing Slips, Delivery Notes & Shipping Labels plugin for WordPress is vulnerable to Insecure Direct Object Reference in versions up to, and including, 5.0.2 via the 'email' parameter of the guest print_document_from_the_mail_link handler dispatched from print_window() on init. This is due to the handler authorizing access to an order's printable documents when the attacker-supplied (base64-encoded) 'email' equals the order's billing email — a non-secret identifier — instead of requiring the WooCommerce order_key. This makes it possible for unauthenticated attackers, when the site is configured to allow guest access to documents ('wt_pklist_print_button_access_for' != 'logged_in'), to retrieve any other customer's invoice, packing slip, delivery note, dispatch label or shipping label — including customer name, billing/shipping address, phone number, purchased products, prices, taxes and invoice metadata — by knowing the target order ID and the associated billing email address.