Hacking APIs: Exploiting Shadow APIs and Forgotten Endpoints

Most companies focus on protecting their main APIs. But attackers know that the real gold often hides in places security teams forget: old versions, testing endpoints, internal routes, and unprotected documentation.

These are called Shadow APIs. They are APIs not listed in official documentation or not monitored. Shadow APIs are dangerous because they can leak sensitive data or allow access without proper security.

In this article, we’ll explore how attackers find and exploit these shadow APIs, with real examples of requests and responses.

What is a Shadow API?

A Shadow API is any API endpoint that:

• Is not documented or monitored
• Comes from a previous app version (e.g., /api/v1/)
• Was used in staging/testing but left active
• Exists in legacy frontend code or mobile apps

Attackers search for them because they are often forgotten, weak, or unprotected.

Finding Shadow APIs with Wordlists

Attackers use tools like ffuf, dirsearch, or httpx to brute-force API paths.

Example command:

ffuf -w wordlist.txt -u…