Part 9 — API Endpoint Analysis

Master the art of dissecting API endpoints to uncover hidden vulnerabilities and security flaws

🎯 Overview

Endpoint analysis is where reconnaissance meets exploitation. After discovering API endpoints, the next critical phase is understanding how they work, what data they expose, and where security controls fail. This phase bridges passive discovery and active exploitation.

What You'll Learn:

Extracting actionable intelligence from API documentation
Reverse engineering undocumented APIs
Identifying information disclosure vulnerabilities
Spotting excessive data exposures
Detecting business logic flaws

📚 Finding & Leveraging API Documentation

Quick Documentation Hunting

Common Documentation Paths:

/docs
/api/docs
/documentation
/api-docs
/swagger
/openapi.json
/redoc
/graphql (for GraphQL APIs)

Pro Tip: Use directory fuzzing with API-specific wordlists:

# Using ffuf
ffuf -u <https://target.com/FUZZ> -w api-endpoints.txt

# Check GitHub for exposed specs
site:github.com "target.com" (openapi OR swagger OR "api documentation")

Key Documentation Elements

Focus on these critical sections:

Element	What to Extract	Why It Matters
Authentication	Methods, token formats, required headers	Identifies auth bypass opportunities
Endpoints	Full paths, HTTP methods	Maps attack surface
Parameters	Required/optional, data types, constraints	Reveals input validation gaps
Error Responses	Status codes, error messages	May leak sensitive information
Rate Limits	Request quotas, time windows	Helps plan brute-force attacks