The Bahn currently has a Web-based game for you to win some of their loyalty points. It’s not a very exciting game, but you get up to 500 points which is half a free ride across the country. (You get the other half when signing up for their program.)
In order to get these 500 points you need to play for an hour or so. Or you observe the Web traffic your browser generates and look closely. You’ll see that the Flash applet fetches a token from the server and sends your result, along with the token and some hash, to the server. How to get the correct hash you ask? Worry not, you will get the correct hash from the server if you don’t send the correct one. You can resend your request with the hash the server sent you and your POST will be accepted. Neat.
I don’t know why they send the “correct_hash”, but it’s obviously a bad idea.
PS: It seems that Kazam has troubles recording my mouse pointer position correctly.