For regular download WUpload generates download links containing some hash based on a browser session info (session ID, referrer, cookies etc.) and compares that hash with session info returned by FDM (which is different than the browser info).

And because you are not developers FDM information session with the beat of your browser?

Now it's serious ... File hosting sites really suck. All that needed to happen is download the right file. The guys hate file managers? Have them tell their mothers as purchases that people want to download files!