http://us63bgjkxwpyrpvsqom6kw3jcy2yujbplkhtzt64yykt42ne2ms7p4yd.onion/graves/news/2019-03-14-firefox_send.html
Time spent, clicks, referrer information - very private indeed. Now the technical data : This includes information such as operating system, browser, language preference, country, timestamps, duration for file transfer, reasons for errors, reasons for file expiration.