Flash is a very powerful tool for making video games. Yet, as with other games, there will be players who will try to cheat. That's why it's a smart decision to disable the right click menu in Flash. To do that, simply add the follow line of code in the first frame of your movie.
Code:
Stage.showMenu = False;
That's all there is to it. Simply export your Flash project to .swf, load it up, then right click the screen. A menu should still appear, but the Zoom, Play, Forward and many other commands will be disabled. This prevents players from skipping certain parts of your game. It also prevents the players from causing weird errors to happen, as rewinding and playing a Flash Game can have undesired results.
Players might be able to compromise your game, if they are allowed menu control.