✍️ Introduction
Most hunters look for technical bugs:
- XSS
- SQLi
- SSRF
But some of the highest payouts come from something else:
👉 Breaking how the system is supposed to work
No injection. No payload tricks.
Just:
💥 Abusing logic to create real financial loss
🧠 The Goal of This Walkthrough
We're not just finding a logic flaw.
We're turning it into:
👉 direct financial impact
🧭 The Scenario (Realistic)
You're testing an e-commerce application.
Checkout flow:
- Add item
- Apply coupon
- Pay
🔍 Step 1 — Understand the Flow
Captured request:
POST /apply-coupon
code=DISCOUNT10👉 Works once (as expected)
⚠️ Most Hunters Stop Here
They confirm:
- Coupon works
- No obvious issue
👉 And move on
🧠 Step 2 — Break the Assumption
Ask:
👉 "What if I send this multiple times?"
🔑 Step 3 — Replay the Request
You send:
POST /apply-coupon
code=DISCOUNT10Multiple times in quick succession.
👉 The system applies it multiple times
📸 Screenshot — Coupon Applied Multiple Times
💥 Step 4 — Escalate the Impact
Now:
- Price = 100
- Discount = 10%
After multiple requests:
👉 Price drops to near 0
💥 Financial abuse confirmed
🔥 Step 5 — Combine With Timing (Race Condition)
You send:
👉 Multiple coupon requests at the same time
System processes all of them.
👉 Discount applied repeatedly without validation
💥 Critical impact
🧭 What Just Happened
You chained:
- Business logic flaw (no limit enforcement)
- Request replay
- Race condition
👉 Final result:
💥 Direct financial loss
⚠️ Why This Is High Severity
Because it affects:
- 💳 Revenue
- 📦 Orders
- 💰 Business operations
👉 This is what companies care about most
⚠️ Common Mistakes
❌ Only testing once ❌ Trusting UI restrictions ❌ Not replaying requests ❌ Ignoring timing attacks
🧠 Pro Techniques
🔑 1. Always Test Repetition
If something should happen once:
👉 Try it multiple times
🔑 2. Skip Steps
Try:
POST /checkoutWithout applying coupon normally
👉 Backend may not validate flow
🔑 3. Modify Values
Change:
price=100 → price=1
quantity=1 → quantity=10👉 Check if backend trusts client
🔑 4. Target Refunds & Credits
High-value targets:
- Refund systems
- Wallet credits
- Gift cards
👉 Often vulnerable
🔑 5. Combine With Race Conditions
Logic flaw + timing:
👉 Extremely powerful
💥 Real Impact Scenario
Refund endpoint:
POST /refund
order_id=123You send 5 requests at once.
System processes all 5.
👉 You get refunded 5 times
💥 Direct financial loss → Critical vulnerability
🧭 Why This Changes Your Level
Because:
👉 You're no longer finding "bugs"
👉 You're creating real-world impact
🚀 What's Next
👉 Next post:
🧠 How I Actually Hunt — The Ghostyjoe™ Workflow
⚠️ Ethical Use Disclaimer
This content is for educational purposes only.
Only test systems you are authorized to test.
👏 Before You Go
If this helped you:
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