API Security

Penetration testing for APIs

An API has no interface to hide things behind. Permissions, response structure and parameters are the defense itself — and that's where the significant vulnerabilities live.

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What we test in APIs

Object-level authorization

Does changing an ID in a request return data belonging to another user, organization or customer?

Function-level authorization

Is an admin endpoint or privileged action reachable by a user with a regular role?

Authentication and token management

Expiry, refresh, revocation, and how the system handles an expired or re-crafted token.

Data exposure in responses

Internal fields, other users' data or information the consuming client doesn't need.

Parameter validation

Handling of unexpected input, filtering, pagination, sorting and rate limits where relevant.

Documentation vs. reality

Comparing the API specification with the endpoints actually available, including old versions left open.

What helps make the test precise

A list of user types and roles, and what each role should be able to see
OpenAPI / Swagger documentation or a request collection (Postman)
Separate test accounts per role, and two organizations to test isolation
Business context: what counts as a sensitive action in your system
A definition of what's out of scope, including third-party providers

Why business context is critical in APIs

An endpoint that returns data can look technically perfect and still expose information that shouldn't be available to that role. Tools don't know your business rules; a human tester who understands the model can identify and validate that kind of gap.

That's why the test uses multiple accounts and roles, and checks what each of them can actually achieve within the approved scope.

Deep dive into the API security testing process →

API testing FAQ

We don't have API documentation. Can you still test?

Yes. We can work from the application's traffic and an explanation from your team. Documentation or a request collection shortens the ramp-up and improves coverage within a given time.

Do you need multiple environments or accounts?

Testing data isolation requires at least two separate accounts, ideally two organizations or tenants. Without that, some authorization tests can't be performed meaningfully.

Is API testing included in the application test?

It's included when it's defined in the agreed scope. The scope can be Web only, API only, or a combination.

Let's understand what needs testing in your API

Send your details and we'll get back to you to define a precise scope.