This isn't a bug. The validation that they are doing when you enter the card is just Luhn validation.§ This is basically just to ensure that the numbers enter

This isn't a bug. The validation that they are doing when you enter the card is just Luhn validation.§ This is basically just to ensure that the numbers entered into the field "at least have the possibility of being a valid credit card". No processing of the card is being done at this stage. § - http://en.wikipedia.org/wiki/Luhn_algorithm http://en.wikipedia.org/wiki/Luhn_algorithm