Flappy Sonic already hacked

My flappy bird clone has already been hacked by someone who scored 9999 points. Since this is a highly unprobable score for a casual player it's obvious that the game has ben hacked.

This is really easy since the hiscore is sent in plain text directly through a websocket, you can do it directly using the web inspector.

How can you avoid this?
Here you can read some general advices dealing with security while using websockets but I wont be implementing them for now since I don't have enough free time for this.

Don't be evil! :)