I haven't secured my MMCodes script (i.e. people can type +99999- in the bank to recieve unlimited money/crystals).
As my MMCodes is only v2.0 and I do not have the time to secure this, but I have secured my paid modifications 100%.
However this Deal or No Deal has been tested by many users and has not had a single bug, and I guarantee there is no security flaw in this.
Edit:
It is supposed to be like this, the money in your box is the money you exclude from the game, if you need an example, here is one:
http://www.unoriginal.co.uk/deal-or-no-deal.html