Why API security is different (and why it matters)

Two months since I joined Detectify and I’ve realized something: API security is a completely different game from web application security. And honestly? I think a lot of teams don’t see this yet.

APIs are everywhere (but you might not know where)

Let’s look at the modern application. Your mobile app? APIs. Your crucial SaaS integrations? APIs. That complex checkout flow? Probably five or more API calls talking with each other. Modern applications are, fundamentally, just APIs talking to other APIs with a fancy UI layered on top.

But here’s what’s been catching me off guard: many companies don’t even have a complete inventory of their APIs. You’re trying to secure a perimeter you can’t even see the edges of. I have seen:

• Shadow APIs: Old endpoints no one remembers deploying.
• Zombie APIs: Test/staging endpoints that never got turned off.
• Partner APIs: Third-party integrations that extend your attack surface.

How can you secure what you can’t see?

The attack vectors are different

When we talk about web vulnerabilities, usually we’re dealing with XSS, CSRF, clickjacking – stuff that messes with what users see or tricks them into clicking something they shouldn’t. API vulnerabilities are a different beast. We’re talking broken authentication, APIs exposing way too much data, weak rate limiting, injection attacks. 

These attacks skip the UI entirely. An attacker doesn’t need to trick a user into clicking something malicious. They just need to understand your API contract and find the weak spots. That’s it. The scary part? They can automate all of this.

Authentication is… well… complicated

Web apps usually use session-based authentication with cookies. It’s pretty standard, most frameworks handle it well, and there are well-known patterns to follow. APIs? That’s where things get messy. OAuth, JWT, API keys, mutual TLS, custom bearer tokens… There are so many different approaches, and each one has its own vulnerability patterns. I’ve been diving deep into the OWASP API Security Top 10, and honestly, the auth issues are wild. Broken Object Level Authorization, Broken Function Level Authorization… these things have scary-long names, but they’re everywhere. Even though everyone knows about them, they still pop up in production all the time.

Why does it matter?

API attacks are growing at an alarming rate for several reasons:

1. Automation is Easy: APIs return structured data that is easier to parse than HTML, making it suitable for automation. This is great for developers, but even more perfect for attackers. 
2. Weak Rate Limiting: Since APIs need to handle high-volume traffic, rate limiting is often weaker.
3. Documentation as Blueprints: API documentation, while great for developers, also serves as a perfect attack blueprint, showing adversaries exactly where to poke.

This is exactly why we’re constantly enhancing our API Scanning capabilities at Detectify, because understanding these blind spots is the first step to fixing them.

How does your team handle this?

We’d love to hear how other teams are tackling this complex problem.

• How do you maintain a complete, up-to-date inventory of ALL your endpoints, including the “zombie” ones?
• What’s your strategy for testing authorization at scale when you have hundreds of different endpoints and authentication methods?
• How do you approach API versioning and deprecation without accidentally leaving critical security holes in old versions?
• What API security challenges keep you up at night?

FAQ

Q: What is the primary difference between web application security and API security?

A: Web application security often focuses on user-facing vulnerabilities like XSS, while API security is concerned with flaws like broken authentication and weak access control that attackers can exploit by directly interacting with the API endpoints, bypassing the UI.

Q: What are Shadow and Zombie APIs?

A: Shadow APIs are old endpoints that are forgotten but still deployed, while Zombie APIs are test or staging endpoints that were never turned off, and both extend the attack surface without the organization’s knowledge.

Q: Why are API attacks easily automated?

A: API attacks are easily automated because APIs return structured data (like JSON or XML) that is much easier for a script or bot to parse and manipulate than the more complex and varied structure of HTML pages.