The WPC Product Bundles for WooCommerce plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'qty' parameter in all versions up to, and including, 8.6.6 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 page. The float cast used during quantity validation allows a numeric-prefixed payload such as '1 ' to pass validation while retaining its malicious HTML, which is then stored verbatim in order item metadata under the '_woosb_ids' key.