API Penetration Testing

Why APIs Are a Growing Attack Target

Modern applications are heavily API-driven. Mobile apps, single-page applications, third-party integrations, and microservices architectures all rely on APIs to function. This means that an application's business logic — and its most sensitive data — is increasingly accessible through API endpoints that may receive far less security scrutiny than the visible front-end.

What API Penetration Testing Covers

• Authentication and authorization — Can an unauthenticated user call API endpoints? Can an authenticated user access resources belonging to other users?
• Broken object level authorization (BOLA/IDOR) — The most common and impactful API vulnerability: changing an ID in a request to access another user's data
• Excessive data exposure — Do API responses return more data than the client interface displays?
• Rate limiting and resource exhaustion — Can the API be abused to enumerate users, brute-force credentials, or cause denial of service?
• Mass assignment — Can API parameters be manipulated to write to fields that should be read-only?
• Injection in API parameters — SQL, command, and other injection vulnerabilities via API request bodies and query strings

REST, GraphQL, and SOAP

Grid32 tests all common API architectures: RESTful APIs, GraphQL endpoints (including introspection abuse and query depth attacks), and legacy SOAP-based web services. Each architecture has a distinct attack surface, and our engineers are experienced with all of them.