> the final part of the blog post indicates that the person intends to 'test it'.

Someone testing the hack could buy two of the same item, one of which has the hacked barcode. The tester could then immediately point out the error, so no fraud actually occurs. A better way of doing this might be to use two people pretending to be a couple, with the first person checking out separately with the correct price. Then the second person could check out with the hacked barcode, then immediately point out the error.

This also gives a good control for the "experiment."