Do you mean fake vaccine cards? If that's it then....
It will happen eventually but will you really jeopardize your own health just to go to the mall and satisfy the need to feel the comfort of an airconditioned space?
I was worried about this too but when I saw the QR code in the card then it gave me a bit of a relief. That's authentication. Though, it will depend on the security of the establishment if they will produce machines that will authenticate the legitimacy of it. I think they should for everyone's safety.
I am just outside once every couple of weeks for necessities and the grocery is still not looking for the card as long as you wear your mask.