They Paypal IPN uses some functions to set prices based on how many points they are wanting to get. Basically it doesn't send any post data except the amount of points they want to get and does some math to get the value so they can't just edit an input to set the price of the item. I didn't make it so if you would like to test it for exploits you may do so. If you find any tell me so I can fix them. I can't really find anything wrong with it by just looking but my knowledge of PHP is pretty basic. Any bugs or exploits in the shop itself if you would like to tell me about so I can fix I would love some feed back on. Other then that no one has reported anything so as far as I know it is 100%.