The WooCommerce PDF Invoices, Packing Slips, Delivery Notes and Shipping Labels plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the Customer Notes field in all versions up to, and including, 4.4.1 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected invoice for printing.