Double Redeem Race

Scenario

GiftDrop credits one hundred dollars when you redeem code GIFT100. The wallet update reads balance, adds credit, then writes back without locking. Fire parallel redemptions so the same code pays out twice.

Your approach

1. Reset the lab wallet if needed and note starting balance.
2. Use the parallel redeem button or send many simultaneous POST requests.
3. Refresh balance until it shows at least two hundred dollars.
4. Copy the race success flag from the page.
5. Submit the double-redeem flag.