API Security Testing

API security testing protects the part of your product that attackers target most. Modern web and mobile apps rely on APIs to move sensitive data, and a single broken authorisation check can expose every customer record. Our testers manually assess your APIs against the OWASP API Security Top 10 and real-world attack techniques.

What We Test

• Broken object level authorisation (BOLA/IDOR) and broken function level authorisation.
• Authentication: JWT, OAuth 2.0, API keys, token expiry and refresh flows.
• Excessive data exposure and mass assignment.
• Injection and server-side request forgery (SSRF).
• Rate limiting and resource abuse, including business flow abuse.
• GraphQL-specific issues: introspection, batching and query depth attacks.

Our Approach

We work from your API documentation, Postman collections or OpenAPI/Swagger specs, and from traffic captured through your apps. Each endpoint is tested with every relevant user role so we can find authorisation gaps that automated tools miss. REST, GraphQL, SOAP and gRPC APIs are all in scope.

What You Get

• Executive summary plus endpoint-level technical findings.
• Proof-of-concept requests and responses for every issue.
• Prioritised remediation guidance for your developers.
• A free retest and an updated report once fixes are deployed.

Why Offensium Vault

• Deep API expertise from years of security research and bug bounty work.
• Manual authorisation testing across all roles and tenants.
• ISO 27001 and ISO 9001 certified delivery.

APIs are usually tested together with web application penetration testing or mobile app penetration testing. Read more in our API security assessment guide.

Frequently Asked Questions

What do you need from us to start?

API documentation or a Postman/OpenAPI collection, test accounts for each role, and the target environment details.

Do you test GraphQL APIs?

Yes. We test GraphQL schemas for introspection exposure, authorisation flaws, batching abuse and denial-of-service through complex queries.

Is API testing included in VAPT?

It can be. We often scope APIs as part of a wider VAPT engagement or as a dedicated assessment.

Get a Quote

Tell us about your environment and timelines and we will send a clear, fixed-scope proposal. Contact Offensium Vault or book a free call with our team.