Whenever two people are on my website using the cart simultaneously, and they add items to the cart, the other user can see all the items of the other person's cart. The items stay there until a person clears the cart, or an order is placed and the cart is cleared. As well, one person can see another person's credit card info, name, address, phone, etc, if two people or more are using at the same time.
What can fix this?