The Extra Product Options Builder for WooCommerce WordPress plugin before 1.2.176 does not verify that the requester is entitled to a customer-uploaded file before serving it, allowing unauthenticated users who obtain a file's stored name to retrieve it.
The Extra Product Options Builder for WooCommerce WordPress plugin before 1.2.176 writes a deny-all rule into its upload directories, so the disclosure only crosses a boundary on web servers that honour it, such as Apache. Where it is ignored, as on a default nginx setup, the same files are already served at their direct URL and the endpoint exposes nothing further.