Hacking Starbucks to get unlimited coffee

Nice bugs. Race conditions are fun. Different race conditions were posted here a couple weeks ago as well for those who don't know[0].

Race conditions for stuff like "gifts" and "credit/debit" is generally an afterthought and REALLY obvious to bug hunters. It takes less than a minute to create PoC code to perform the attack. This one is actually really slick.

[0] - https://news.ycombinator.com/item?id=9443867

Starbucks behaviour in this case is very bad. You have discovered a serious bug, showed them and they treat you like a criminal !