✍️ Introduction

Most beginners focus on:

  • XSS
  • SQLi
  • Automated scans

But the real money in bug bounty often comes from something else entirely:

👉 Business Logic Bugs

These are not technical mistakes.

They are design flaws in how the application works.

And they are:

  • 💰 Extremely high value
  • 🧠 Harder to detect
  • 🔥 Rare → less competition

🧠 What Is a Business Logic Bug

A business logic bug happens when:

An application behaves in a way that breaks its own rules

🧪 Simple Example

A site allows:

👉 One coupon per user

But you apply it multiple times:

💥 Discount abuse = vulnerability

🎯 Why These Bugs Pay So Much

Because they directly impact:

  • 💳 Money
  • 🎟️ Rewards
  • 📦 Orders
  • 📊 System integrity

👉 Companies care A LOT about this

🔍 Where to Look (Real Mindset)

Stop thinking:

❌ "Where is the vulnerability?"

Start thinking:

👉 "How is this supposed to work… and how can I break it?"

Look at:

  • Checkout flows
  • Coupons / discounts
  • Subscriptions
  • Refund systems
  • Account limits
  • Booking systems

📸 Screenshot — Checkout Flow Testing

🛠️ Step-by-Step Testing (Real Approach)

1. Understand the Flow

Example:

  1. Add item
  2. Apply coupon
  3. Checkout

👉 Map every step

2. Intercept Requests

Use Burp to capture:

POST /apply-coupon
POST /checkout

3. Break the Rules

Try:

  • Applying coupon multiple times
  • Skipping steps
  • Replaying requests
  • Changing values

4. Observe Behavior

If system allows something it shouldn't:

💥 Business Logic flaw

📸 Screenshot — Coupon Abuse Example

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⚠️ Common Mistakes

❌ Only relying on automated tools ❌ Not understanding the application ❌ Testing only once ❌ Ignoring edge cases

🧠 Pro Techniques (This Is Where You Win)

🔑 1. Replay Requests

Send the same request multiple times:

👉 Sometimes actions repeat (double purchase, double refund)

🔑 2. Skip Steps

Try jumping directly to:

POST /checkout

Without previous steps

👉 System might not validate flow

🔑 3. Modify Values

Change:

price=100 → price=1
quantity=1 → quantity=10

👉 Check if backend validates

🔑 4. Race Conditions

Send multiple requests at once:

👉 Double spend / duplicate actions

🔑 5. Abuse Limits

If system says:

👉 "1 per user"

Try:

  • Multiple requests
  • Multiple sessions
  • Timing attacks

💥 Real Impact Scenario

A site allows refunds:

POST /refund
order_id=123

You send it twice quickly:

👉 You get refunded twice

💥 Financial loss → Critical bug

🧭 Why This Is So Powerful

Because:

  • No scanner will find it
  • No template exists
  • Requires thinking, not tools

👉 This is where real hunters stand out

🚀 What's Next

👉 Next post:

💉 Injection Attacks — From Input to Full System Control

⚠️ Ethical Use Disclaimer

This content is for educational purposes only.

Only test systems you are authorized to test.

☕ Support

👉 https://buymeacoffee.com/ghostyjoe

👏 Before You Go

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🎯 Series

This is Part 4 of:

👉 15 High-Value Bug Classes That Actually Pay