API Penetration Testing
API & Web Service Penetration Testing
API Penetration Testing API & Web Service Penetration Testing APIs are the connective tissue of modern applications — and a prime target for attackers. We test your REST, GraphQL and SOAP APIs against the OWASP API Security Top 10, combining automated tooling with in-depth manual testing to uncover flaws in authentication, authorisation and business logic that scanners alone will miss.
Overview
What is API penetration testing?
API penetration testing is a focused security assessment in which our consultants probe your application programming interfaces for vulnerabilities — broken object-level authorisation, weak authentication, excessive data exposure, injection and misconfiguration — that could let an attacker access data or functions they should never reach.
Because APIs expose business logic directly, small oversights can have a large impact. We give you a clear picture of your real-world risk and prioritised, practical remediation guidance so issues are resolved before they are exploited.
What you'll receive
- ✓Scoping: agreed REST, GraphQL or SOAP endpoints, schemas and authentication flows
- ✓Testing: manual testing against the OWASP API Security Top 10, including authorisation and business logic
- ✓Executive report: an API risk summary for stakeholders and decision-makers
- ✓Technical report: findings rated by CVSS with full request/response evidence
- ✓Remediation: fix guidance for your API framework, gateway and access controls
- ✓Retest & debrief: a retest of fixes and a walkthrough call with your developers
Why It Matters
The value of regular security reviews
Evaluate your controls
Regular security reviews enable organisations to comprehensively evaluate their security measures, including the effectiveness of controls, configurations, and policies.
Strengthen your posture
Identifying weaknesses allows organisations to strengthen their security posture and better protect their assets and data against evolving threats.
Meet compliance
Regular security assessments are essential for compliance with industry regulations and data protection laws, demonstrating your commitment to a secure environment.
High-Level Methodology
A structured, five-phase approach
Scoping & Setup
We agree the APIs and endpoints in scope and gather what we need to test thoroughly — documentation such as an OpenAPI/Swagger specification, a Postman collection, and test credentials for each user role.
Endpoint Discovery & Mapping
We map every endpoint, method and parameter — including undocumented and deprecated routes — building a complete picture of the attack surface before deeper testing begins.
Authentication & Authorisation Testing
We test token handling, session management and object- and function-level access controls, probing for broken authorisation and privilege escalation between users — the most common and damaging API flaws.
Injection & Logic Testing
We test for injection, mass assignment, excessive data exposure, weak rate limiting and business-logic flaws, verifying each finding manually to confirm real-world impact.
Analysis & Reporting
We rate each finding by real-world risk and deliver a clear report with reproduction steps and prioritised remediation guidance, and we are happy to retest once fixes are in place.
FAQ
Frequently asked questions
Which API types and standards do you test?
We test REST, GraphQL and SOAP APIs, as well as gRPC and WebSocket services on request. Our methodology follows the OWASP API Security Top 10 and we make use of your API documentation, such as an OpenAPI/Swagger specification, where available.
How much does an API penetration test cost?
Cost depends on the number of endpoints in scope, the number of user roles and the complexity of the business logic and integrations. Contact us for a customised quote.
What information is required to scope a test?
To accurately scope a penetration test, we typically need information about your network range (IP addresses), domain names, key systems and applications, and any specific security concerns you have.
Do you need access to our API documentation?
Documentation such as an OpenAPI/Swagger specification, a Postman collection and test credentials helps us achieve thorough coverage efficiently. We can also test with limited documentation, using discovery techniques to map your endpoints, though this may take longer.
What are the most common issues you find?
Recurring findings include broken object- and function-level authorisation, weak authentication, excessive data exposure, mass assignment, missing rate limiting, and business-logic flaws — in line with the OWASP API Security Top 10.
Ready to secure your APIs?
Get a fast, transparent quote for your API assessment, or talk to a consultant about scoping the right engagement.