Lab 177 — CartNova — Race Condition in Coupon Redemption

hackadvisor

Task: Express.js e-commerce app with WELCOME100 coupon ($100) and premium product ($499.99); coupon redeem endpoint has non-atomic check-then-update. Solution: fire 300 concurrent threads with threading.Barrier to exploit TOCTOU window, redeem coupon 5× for $500, purchase premium product to get flag.