API Penetration Testing Service
API Security
APIs are a backbone of modern applications – connecting mobile apps, web platforms, and third-party integrations together. They often handle sensitive data and critical business logic, which makes them a prime target for attackers.
Security vulnerabilities in APIs can expose customer data, grant unauthorised access, and enable the abuse of business functionality. Unlike weaknesses in traditional web applications, API security issues often involve authentication bypasses, broken object-level authorisation, and logic flaws that fully automated scanners cannot detect.
API penetration testing validates the security of your REST, GraphQL, SOAP, and custom APIs through manually led security testing. This type of testing is essential for any organisation exposing APIs to mobile applications, third-party integrations, or microservices architectures.
Who Needs API Penetration Testing?
API security testing is essential for:
Regular API testing validates security controls, meets compliance requirements, and protects your business from data breaches and unauthorised access.
What We Test
We go beyond the OWASP API Security Top 10 to ensure comprehensive coverage of your API’s attack surface. Our testing can cover REST, GraphQL, SOAP, and custom API implementations.
Authentication Mechanisms
JWT token validation, API key security, OAuth 2.0 flows, session management, multi-factor authentication bypass, and credential stuffing attacks across all authentication methods.
Authorisation & Access Control
Broken object-level authorisation (BOLA/IDOR), broken function-level authorisation, privilege escalation, horizontal and vertical access control bypass, and role-based access control (RBAC) weaknesses.
Rate Limiting & Abuse Prevention
Missing or insufficient rate limiting, brute force protection, API abuse scenarios, resource exhaustion attacks, and denial of service vulnerabilities.
Input Validation & Injection
SQL injection, NoSQL injection, command injection, XML injection, LDAP injection, and server-side template injection across all API parameters (query, body, headers).
Business Logic Vulnerabilities
Workflow bypass, race conditions, mass assignment, parameter tampering, price manipulation, and API-specific logic flaws that automated scanners cannot detect.
Data Exposure & Leakage
Excessive data exposure from API responses, sensitive data in error messages, information leakage through API endpoints, verbose error handling, and insecure data transmission.
API-Specific Vulnerabilities
GraphQL introspection abuse, GraphQL batching attacks, REST API versioning issues, SOAP injection, API endpoint enumeration, and undocumented API discovery.
Parameter Tampering
Hidden parameter exposure, unintended field modification, privilege escalation through parameter injection, and unsafe object binding.
Security Misconfiguration
CORS misconfigurations, missing security headers, verbose error responses, default configurations, unnecessary HTTP methods, and insecure API documentation exposure.
Our Testing Approach
Manual-First Testing Methodology
While we use automated tools for discovery and baseline checks, every finding is manually validated and exploited by our consultants. We focus on business logic flaws, authentication bypasses, and authorisation issues that automated API scanners miss.
Multi-Role Testing
We test APIs across different authentication and authorisation levels, from anonymous users, authenticated standard users, privileged users, and administrators, to identify privilege escalation and access control vulnerabilities.
Real-World Attack Simulation
We think like attackers by combining vulnerabilities, testing edge cases, exploring undocumented endpoints, and demonstrating actual business impact rather than just theoretical risk.
API Type Coverage
We test all modern API architectures:
Pricing
Pricing depends on the number of API endpoints/GraphQL schema size, functional complexity, user roles, and the testing depth that is required. A fixed price is confirmed after a short scoping review.
Why Choose Exploitr
Manual testing, not scans
Clear reporting and advice
Certified testing team
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Fixed pricing with no surprises
Attack Surface Management
Gain complementary access to the Attack Surface Center platform with your penetration test to manage your vulnerabilities, assets, and track remediation progress.
Most API tests take between 3-7 days depending on the number of endpoints, complexity of the functionality, and API architecture. Testing can be performed against development, staging, or production environments. Reports are delivered within 2 business days of testing completion
Yes, we can reverse-engineer and test undocumented APIs through traffic analysis, endpoint discovery, and behavior observation. However, testing is more efficient and can reduce the time needed for an engagement when OpenAPI/Swagger documentation or Postman collections are provided.
If you have a web application or mobile application that consumes the API, we’d highly recommend focusing testing through one of those services if you do not have API documentation available.
Absolutely. We have extensive experience testing GraphQL implementations including introspection abuse, batching attacks, nested query DoS, authorisation bypass, and GraphQL-specific vulnerabilities beyond standard REST API issues.
We use safe testing techniques and coordinate with your team to minimise risk. However, there is always an inherent risk when performing penetration testing.
If possible, testing should ideally be performed in non-production environments, though production testing can be conducted with appropriate rate limiting and planning.
Yes, we test both public-facing APIs and internal APIs used between microservices, mobile apps, or within your infrastructure. Internal APIs often require VPN access or testing from within your network.
We recommend annual testing at an absolute minimum, with additional testing after major releases, new endpoint additions, authentication handling changes, or wider architectural updates. APIs that change frequently benefit from continuous testing through our pentest-as-a-service offering.
Yes, complimentary focused retesting is included to verify that critical and high-severity vulnerabilities have been properly remediated.