Direct Download for WooCommerce <= 1.19 - Unauthenticated Arbitrary File Read via 'file_id' Path Segment

The Direct Download for WooCommerce plugin for WordPress is vulnerable to Directory Traversal in all versions up to, and including, 1.19 via the (top-level include) function. This makes it possible for unauthenticated attackers to read the contents of arbitrary files on the server, which can contain sensitive information. The product ownership check only verifies that some free, virtual, downloadable product exists on the site — not that the requested file path belongs to that product's configured downloads — making exploitation viable on any WooCommerce site with at least one such product.