McDonald's app bug let people order for free in France

Have tried to contact McDonalds but they did not respond.

It was only 4 or 5 coffees so I deleted the app. Should've chased it harder but didn't have the time.

If they were ordering from a cashier at McDonald's and the cashier got distracted for a minute and somehow forgot to charge them before finishing the order, most of the people that abuse a bug like this would tell them about the mistake. I've been in similar situations plenty of times, where I easily could have gotten something without paying because of a staff oversight, but I always tell them I haven't paid yet. Most people won't suddenly decide to steal something just because they're handed an easy opportunity.

But when the transaction is through an app or a website or something, people are completely willing to abuse errors, and will even go through an obscure process deliberately to cause errors so they can abuse them. When Amazon accidentally sells expensive camera equipment for 99% off on Prime Day, people clamor to steal as much as they can, even though it's a blatant mistake. None of those people legitimately believe the price is intentional, they know they're taking advantage of an error. The ones that get away with it brag about it, and others that missed the chance are jealous that they didn't manage to steal anything.

It's really a fascinating piece of psychology to me, that once there's a "system" in place, abusing holes in it feels like a reasonable thing to do, even if the end result is effectively shoplifting.

Edit: the replies to me are a perfect demonstration.

This looks like the software was missing some internal sanity checks. For example, it was hammered into us at Caltech that any answers we derive need to be sane. If an energy value turned out to be negative, we would have to note on the solution something like "the negative value is clearly wrong but I don't know where my mistake is" or we'd get not just zero credit on the solution, but a negative credit.

Software should have the same sort of checks. It's called "contract programming", the simplest manifestation of which are asserts.