FYI, Google Chrome will do the same thing.

If you record a network packet capture, you will see it communicating with history.google.com. You might also notice that each time you load your browser history, that domain will be contacted to sync your history with Google's servers.

Much of your uploaded data can be seen from here, but you'll need to be logged in to see it: https://myactivity.google.com/myactivity?pli=1