Misprints are no rare occurrence for the Magic market. We've seen them for years in various shapes and sizes, and Khans of Tarkir is no exception.
What may be surprising, however, is just how many problems there seem to be this year. We've seen cards with no power/toughness, cards with no dark ink on them, as well as the usual collection of miscuts and the like.
Here's a new one.
Those are foil commons. And, as you can see, they have the foil. What they don't have is the common attached to them. The person who received this box said they got all their regular foil Uncommons and Rares, but the foil sheet that the Commons were supposed to come on just didn't seem to make it through the whole process before being placed in the box.
Maybe Wizards changed something in the printing process, or maybe we're just getting more anecdotal evidence this year, but the end result is the same: Lots of boxes that don't look like they're supposed to.