Uncover Hidden API Endpoints: The Ultimate Tool for Bug Bounty Hunters

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Introduction

APIs are a goldmine for security researchers, but hidden endpoints often go unnoticed. A new tool automates the extraction of API paths from BurpSuite history, transforming JSON keys into a wordlist for deeper reconnaissance. This article explores how to leverage this tool and other techniques to uncover hidden vulnerabilities.

Learning Objectives

  • Discover how to extract hidden API endpoints from BurpSuite logs.
  • Learn to generate a wordlist from JSON keys for fuzzing.
  • Master advanced API reconnaissance techniques for bug bounty hunting.

1. Extracting API Endpoints from BurpSuite History

Tool: JSON Keys to Wordlist Generator

Step-by-Step Guide:

1. Export BurpSuite History:

  • In BurpSuite, go to Proxy > HTTP History.
  • Right-click and select `Save Items` to export as `.xml` or .json.

2. Run the Tool:

python3 json_wordlist_generator.py --input burp_history.json --output api_wordlist.txt

– This parses JSON keys (e.g., `”user”: “admin”` becomes /user/).

3. Use the Wordlist for Fuzzing:

ffuf -w api_wordlist.txt -u https://target.com/FUZZ -mc 200

– Finds unlinked API endpoints.

2. Discovering Hidden API Paths with FFUF

Command:

ffuf -w /path/to/wordlist.txt -u https://api.target.com/v1/FUZZ -H "Authorization: Bearer TOKEN" -fc 403

Explanation:

– `-fc 403` filters out forbidden responses.
– Combine with extracted JSON keys for better results.

3. Enumerating API Parameters with Arjun

Tool: Arjun

Command:

python3 arjun.py -u https://api.target.com/user --get

What It Does:

  • Tests 13,000+ parameter names for hidden inputs (e.g., ?debug=true).

4. Testing for IDOR Vulnerabilities

Manual Testing:

GET /api/user?id=123 HTTP/1.1 
Host: target.com 
Authorization: Bearer YOUR_TOKEN

Automated Check with Burp:

  • Use `Burp > Intruder` to cycle through `id` values (e.g., 100-200).
  • Look for 200 responses exposing unauthorized data.

5. Detecting Broken Object-Level Authorization (BOLA)

Curl Command:

curl -X GET "https://api.target.com/users/1001" -H "Authorization: Bearer ATTACKER_TOKEN"

Mitigation:

  • Implement proper role-based access control (RBAC).

6. Exploiting Excessive Data Exposure in APIs

Example Vulnerable Response:

{ "user": "admin", "password_hash": "a1b2c3..." }

Fix:

  • Use OWASP API Security Top 10 guidelines to filter sensitive data.

7. Automating API Recon with Postman + Newman

Steps:

1. Export Burp Requests to Postman.

2. Run with Newman:

newman run api_scan.json --reporters cli

– Checks for misconfigurations (e.g., CORS, JWT flaws).

What Undercode Say:

  • Key Takeaway 1: Hidden API endpoints are a major source of high-severity bugs. Automated tools like JSON key extractors streamline reconnaissance.
  • Key Takeaway 2: Fuzzing with custom wordlists increases vulnerability discovery rates by 40% (based on HackerOne reports).

Analysis:

APIs are increasingly targeted due to poor documentation and shadow endpoints. Tools like this bridge the gap between manual testing and automation, making bug hunting more efficient.

Prediction:

By 2025, 70% of web attacks will exploit API flaws, up from 40% in 2023 (Gartner). Researchers who master API recon tools will dominate bug bounty leaderboards.

🚀 Pro Tip: Join Deepak’s WhatsApp Group and subscribe to his YouTube Channel for cutting-edge bug hunting tactics!

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Reported By: Deepak Saini – Hackers Feeds
Extra Hub: Undercode MoN
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