I am not sure if this is the right place for feature requests.
But the UX for the expiry date of credit cards could be improved. It would be nice if the input field prevents the user to type a wrong date format. I have noticed this behavior on the Payment Page and inside the Iframe.
Example for logic:
If the user types the number 3 to 9, it should add a zero in front.
If the user types the number 1 followed by 3 to 9, it should add a zero in front of the number 1.
If the user types the number 0, it should not allow to type a second 0.
It would also be nice to validate the input field after the user switches focus if he typed inside the input. I think this would result in a better experience for the user.
The user input is instantly checked if the form validate method was called. Maybe this behavior could be implemented per input field.