Wally World Wip-off

I don't like shopping at Walmart, even on a good day. There are several reasons for it--the main one is philosophical regarding the way they treat employees; the others are just the annoyances of too many people, not enough check-outs operating, chaos in the parking lot, etc. The only reason I go there every week is because it carries the dog and cat supplies that I prefer for our pets. Well, today I discovered another reason to be wary of Wally World.
Awhile back I received a forward in my e-mail, warning of a scam going on at various Walmart stores. In a nutshell, it said that when a customer uses a credit card at the check-out, "cash back" money was being added to their total without their knowledge. Then the clerk would take the cash and give it to a friend, the next person in line. The customer wouldn't realize what had happened unless he/she made a point of checking the receipt, or until they received their credit card statement--and how could they convince the bank days or weeks after the fact that they hadn't received cash back??
I've received many e-mail warnings over the years, like don't lick envelopes because the glue has rat pee in it; or is it that pop can tops have rat pee on them from sitting in the warehouse? I can't remember--but this particular warning about Walmart, I did file away.
Today I was there getting my weekly stuff, and at the check-out I used my Discover card. On the screen it asked if I wanted cash back and I said NO. If I had been putting stuff back in the cart, I may not have noticed what came next--but I was paying attention. The next screen said: "You have requested $60 back in cash." What???!! I told the clerk what it said and that I did NOT want cash back. "Oh," she replied, "just press 'no'." She was a young woman, didn't seem nervous or strike me as trying to rip me off--so is it the whole Walmart POS system that's pulling these shenanigans? Can the clerk, from his/her side of the register, override your "no" and put "yes" to cash back if you aren't paying attention? I would think that at this time of year, with everyone in a hurry and millions of people shopping for the holidays, this scam could mean big bucks to a lot of employees in a lot of stores.
So when using plastic, carefully read every screen and check your receipts immediately to make sure you haven't been charged for money you never asked for--not just at Walmart, but everywhere. Pass this on to your friends and family (I can always use more readers!)