CyberCode Academy

Course 3 - Mastering Nuclei for Bug Bounty | Episode 7: Exploiting Business Logic Flaws and Achieving Multiple Redemptions


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In this lesson, you’ll learn about:
  • Race conditions — definition & impact: concurrency bugs that occur when multiple requests/threads read/write the same resource simultaneously; often business‑logic flaws (e.g., redeeming a single‑use coupon multiple times) that can cause direct financial loss.
  • Common targets & scenarios: single‑use tokens, gift cards, coupon redemptions, inventory decrements, account balance updates, and other stateful operations that must be atomic.
  • Detection approaches:
    • Identify endpoints that perform state changes (POST/PUT) with weak server‑side atomicity.
    • Look for operations lacking proper locking, transactional guarantees, or server‑side checks.
    • Reproduce by sending many near‑simultaneous requests and observing duplicate successful responses.
  • Nuclei race‑testing (template features):
    • Use method: post (or appropriate method) and set the request body with the token/coupon.
    • Enable concurrency testing with race: true and control parallelism via race-count: (e.g., race-count: 10).
    • Match on success by expecting multiple status: 200 responses or other success indicators to confirm the race exploit.
  • Alternative tooling: Turbo Intruder (Burp) is commonly used for high‑precision, high‑concurrency tests when fine control over timing is required.
  • Practical workflow:
    • Reconstruct the raw request (proxy via Burp).
    • Build and validate a Nuclei template (or Turbo script).
    • Run against a safe/staging target with controlled race‑count.
    • Inspect timestamps/responses to confirm simultaneous requests and duplicated success.
  • Real‑world example & rewards: many real bounties (e.g., HackerOne reports) stem from race exploits that allow multiple redemptions; successful findings can yield high rewards because they directly translate to monetary impact.
  • Mitigations & secure design:
    • Enforce server‑side atomic operations (database transactions, row‑level locking).
    • Use optimistic locking with version checks or strong uniqueness constraints.
    • Implement server‑side one‑time token invalidation that’s atomic.
    • Rate‑limit and monitor suspicious concurrent attempts on critical endpoints.
  • Ethics & safety: only test race conditions on systems you are authorized to test (staging or explicitly in‑scope targets), because aggressive concurrent tests can disrupt services.


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CyberCode AcademyBy CyberCode Academy