Summary
The PDF Invoices & Packing Slips for WooCommerce WordPress plugin from 5.16.2 before 5.16.5 does not properly escape several customer-supplied order fields — including the billing and shipping address values and the customer order note — before they are output in generated invoice and packing-slip documents, allowing unauthenticated users placing guest orders to store a malicious script that executes when a shop administrator views the document, leading to Stored Cross-Site Scripting.