Integer-Underflow

An idle/clicker TCP game whose shop checks affordability against a stale cached balance but deducts from a fresh re-read; racing two sessions as the same user underflows an unsigned long to ~1.8e19 bits and buys the flag.

A food-ordering binary reads chef notes with gets() into a buffer sitting in front of an int price field, letting an overflow set a negative price that makes the order total negative and prints /flag.