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Service 03

API Penetration Testing

Endpoint-by-endpoint testing of the interfaces that carry your data, with a focus on authorization, input handling, and abuse resistance.

Why APIs need their own test

APIs are the quiet infrastructure of a modern business. They move data between systems in real time, hold operations together, and make scaling possible. They also tend to be the least scrutinized part of the estate, because there is no interface to look at and nothing obviously wrong when they work.

That combination — essential, everywhere, and unexamined — is what makes them worth testing on their own terms rather than as a footnote to an application assessment. Our API testing focuses on securing these interfaces so they keep doing their job without becoming the way in.

Thorough endpoint analysis

We assess every endpoint in scope, including the ones your user interface never calls. Undocumented and deprecated endpoints are a recurring source of serious findings precisely because nobody has looked at them since they were written.

Authentication and authorization

We verify that only legitimate callers can reach your API, and that each one can only perform the actions they are entitled to. Broken object-level authorization — one account reading another account's records by changing an identifier — is still one of the most common and most damaging API flaws we find.

Data validation

We test how your API handles data in both directions: whether malformed or hostile input is rejected safely, and whether responses leak more than the caller should be able to see.

Rate limiting and abuse resistance

We confirm your API can absorb abuse — credential stuffing, enumeration, and volumetric misuse — rather than falling over or quietly allowing it.

What you receive

A report that lists each affected endpoint, the request that demonstrates the issue, and the change that fixes it. Findings are ranked by what they actually expose in your environment, so the remediation order reflects your risk rather than a generic score.

Common questions

API Penetration Testing — what clients ask

What do you need from us to test an API?
A specification if you have one — OpenAPI, Swagger, a Postman collection, or even a document — plus credentials for each distinct role. The specification saves discovery time and improves coverage. Where none exists we enumerate endpoints ourselves, which works but spends engagement time on mapping rather than testing.
Is API testing included in a web application test?
Partly. A web application test covers the API the front end actually calls, in the ways the front end calls it. A dedicated API test covers every endpoint and every parameter, including the ones no user interface exposes — which is precisely where forgotten administrative functions tend to live.
Can you test an API that partners consume directly?
Yes, and those are often the highest-value tests. A partner-facing API is a trust boundary between organizations, so authorization failures there expose one customer’s data to another. We test each role against every other role’s resources to establish exactly where that boundary holds.

Strengthen your defenses.

Tell us what you need tested. We’ll come back with scope, timeline, and a fixed price.

Request a quote