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.
https://wpscan.com/vulnerability/ac5d0074-295d-46ee-b2ad-8bfd3ef9917b/