Cart dupe purchase bug

I've run into a strange bug with my recent purchase.

• I initially had a product in my cart, intending to use a special code to get it for free.

• I forgot that item was still in my cart.

• Later, I added a new product to my cart and used a one-time-use code on it.

The bug is that the code applied to both products in my cart, not just the new one. As a result, I now have a duplicate of the product in my library.