We had one connected vending machine in the building. Its credit database was on a remote server, so such hacks would not work. However, if you unplugged its e

We had one connected vending machine in the building. Its credit database was on a remote server, so such hacks would not work. However, if you unplugged its ethernet connector and buy something, then somehow your would get your food/drinks and your transaction was stored into a buffer until the machine went online again. That buffer being in volatile memory, unplugging the power cord of the machine was enough for it to forget you ever bought something.