In Australia, there's two main supermarket chains - Coles and Woolworths. Both have their own loyalty schemes where you earn points per dollar to use for discounts at their stores or to convert to airline miles. How they do it is different.
Coles with their Flybuys program accumulate the points and then you log into the Flybuys portal and redeem them for the cash off, the airline miles, the toaster, or whatever.
Woolworths with their Woolworths Rewards program will, by default, when you have 2000 points or more, deduct $10 from your purchase automatically when you scan the card and the purchase is $10.05 or more. Otherwise, you can set it up so that it won't convert them until some random date in December (for Christmas). If you want the airline miles you can set it up so that every quarter, it will convert multiples of 2000 points to 870 Qantas points.
I don't much care for the Woolworths program because I'd like to choose when I redeem my points, thanks all the same. I ended up switching it to Qantas points because, hey, 870 Qantas points is better than 0 Qantas points and no more random surprise discounts when I do, say, my grandmother's shopping.
Recently, Woolworths ran a promo where if you were a new user, you could get 5000 points for signing up for their Rewards promo. Some users on Ozbargain did and noticed that they didn't have the points on their account... but they had been used already, at stores located nowhere near them.
If you download the Woolworths Money app (for their store branded credit cards) you can plug in any Rewards card number and you will see the balance, no login needed.
Once you have the barcode number with a known good number of points, all you then need to do is add the account to Android Pay, Stocard or a similar app that stores loyalty cards, and then claim the points on your own shop. Boom. Easy money.
It appears that the card numbers on the barcode on the card are simply generated in sequence, with the last digit as a check number as per virtually other barcode, meaning that it would not be overly difficult for a determined person to find a card with a good number of points on it.
Apparently, when designing their system, nobody thought that on the spot redemptions could possibly be abused in anyway, a notion I'm sure they're now relieved of.