✍️ Introduction

Modern applications are no longer just websites.

They are:

👉 APIs everywhere

  • Mobile apps
  • Single Page Apps (SPA)
  • Microservices
  • Third-party integrations

And where there are APIs…

👉 There are vulnerabilities.

🧠 What Are API Vulnerabilities

API vulnerabilities happen when:

Backend endpoints expose data or functionality without proper security controls

🧪 Simple Example (BOLA)

GET /api/user/1001

Change to:

GET /api/user/1002

If you get another user's data:

💥 Broken Object Level Authorization (BOLA)

🎯 Why API Bugs Pay So Well

Because APIs often:

  • Handle sensitive data
  • Control core functionality
  • Are less protected than UI

👉 One API bug can expose everything

🔍 Where to Look (Real Mindset)

Think:

👉 "What is the frontend calling?"

Look at:

  • /api/
  • /v1/
  • /v2/
  • /graphql
  • Mobile app endpoints

📸 Screenshot — API Requests in Burp

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🛠️ Step-by-Step Testing

1. Capture API Traffic

Use:

  • Burp Proxy
  • Browser DevTools

2. Identify Endpoints

Example:

GET /api/v1/orders/123

3. Modify Parameters

Try:

/orders/124
/orders/125

4. Analyze Response

If data changes without checks:

💥 API vulnerability confirmed

📸 Screenshot — JSON Data Exposure

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⚠️ Common Mistakes

❌ Only testing the frontend ❌ Ignoring hidden endpoints ❌ Not modifying IDs ❌ Not testing POST/PUT

🧠 Pro Techniques (Where Real Bugs Are Found)

🔑 1. BOLA / IDOR in APIs

Change IDs in:

/user/1001 → /user/1002

👉 Very common

🔑 2. Mass Assignment

Send extra fields:

{
  "role": "admin"
}

👉 If accepted → privilege escalation

🔑 3. Missing Authorization Checks

Remove:

  • Tokens
  • Headers

If still works:

💥 Critical issue

🔑 4. GraphQL Abuse

Query more data than intended:

👉 APIs often overexpose data

🔑 5. Verb Tampering

Change:

GET → POST  
POST → PUT

👉 Some endpoints are poorly protected

💥 Real Impact Scenario

API request:

GET /api/v1/account/2001

Change to:

GET /api/v1/account/2002

Response returns:

  • Email
  • Address
  • Orders

👉 Accessing another user's data

💥 High / Critical vulnerability

🧭 Why This Matters

Because APIs are the backbone of modern apps

If they are insecure:

👉 Everything is exposed

🚀 What's Next

👉 Next post:

⏱️ Race Conditions — Exploiting Timing for Real Impact

⚠️ 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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