It is said that the Facebook version was removed due to hacks, but that's impossible.
In fact the Android version is much easier to hack, because they can get into the dll files which makes a Unity game, it's like that with all Unity games. However with Facebook, it was server sided, you couldn't save the source files, couldn't download the game, couldn't get into the dll's or anything. The Android version was hack infested, not Facebook.
The only possible thing you can do to cheat in the Facebook embedded version was make a bot to race for you, which isn't any sort of autowin and would be inconsistent.
Reason why I made this thread is because I recently started learning about Unity game hacking, and spoken to a few people. They couldn't hack the Facebook game the same way as they are messing with the Android version. The Android version is literally super easy to hack, there's a program which edits dll's, then you save that dll, package it up and install it on your device.
I don't have experience from when the Facebook version was up, but I was told that it was the most secure of the bunch!