APIPenetrationTesting
APIs are where your business logic and customer data live, and where the most critical vulnerabilities hide. We deliver CREST-accredited API security testing across REST, GraphQL, and SOAP, targeting the authorisation flaws, logic errors, and token vulnerabilities that automated scanners cannot detect. OWASP API Security Top 10 mapped. Results delivered as we find them. Final report within days after test completion.
API Penetration Testing Methodology
Focused on the OWASP API Security Top 10 (2023), our API security testing methodology targets the logic, authorisation, and protocol-specific flaws unique to API architectures. Every engagement covers all ten OWASP categories, from BOLA (API1) and Broken Authentication (API2) through to Server Side Request Forgery (API7) and Unsafe Consumption of APIs (API10). Findings are mapped to OWASP categories in the final report.
Authorisation Testing (BOLA/IDOR)
The most common and critical API vulnerability. We rigorously test for Broken Object Level Authorisation (BOLA) to ensure users cannot access or modify resources belonging to others by simply changing an ID. Every endpoint is probed for horizontal and vertical privilege escalation across multi-tenant object hierarchies.
Mass Assignment & Logic Flaws
Testing for mass assignment vulnerabilities where internal object properties (e.g., 'isAdmin': true, 'balance': 1000) can be overwritten by external input. We also validate business logic constraints across complex multi-step workflows, targeting the flaws that automated DAST scanners cannot model.
Authentication & Token Security
Assessing authentication mechanisms including JWTs, OAuth 2.0, and API keys. We test for weak signing secrets, token leakage, algorithm confusion attacks, lack of expiration, and bypassable authentication checks.
Injection & Input Validation
Testing for SQL injection, NoSQL injection, command injection, and XML External Entity (XXE) attacks. APIs often process structured data directly, making them susceptible to injection if input validation is weak.
Rate Limiting & Resource Consumption
Verifying that appropriate rate limiting is in place to prevent brute force attacks, denial of service (DoS), and automated scraping of sensitive data. Mapped to OWASP API4:2023 Unrestricted Resource Consumption.
GraphQL, SOAP & Protocol-Specific Testing
Protocol-aware testing beyond generic API checks. GraphQL: introspection data exposure, nested query denial of service, batched mutation attacks, and field-level authorisation bypass. SOAP: WSDL enumeration, injection via SOAP envelope, and XXE attacks. REST: HTTP verb tampering, parameter pollution, and shadow API discovery.
OWASP API Security Top 10 Coverage
Every engagement tests against all ten OWASP API Security Top 10 (2023) categories. Every finding in the report is tagged to its corresponding category for audit evidence.
Broken Object Level Authorisation
BOLA testing across every endpoint, including multi-tenant object hierarchies.
Broken Authentication
JWT algorithm confusion, token leakage, OAuth 2.0 bypass, and session fixation.
Broken Object Property Level Authorisation
Mass assignment attacks and excessive data exposure in API responses.
Unrestricted Resource Consumption
Rate limiting bypass, payload flooding, and nested query denial of service.
Broken Function Level Authorisation
Admin endpoint discovery, HTTP verb tampering, and privilege escalation.
Unrestricted Access to Sensitive Business Flows
Multi-step logic abuse, account takeover flows, and automated process exploitation.
Server Side Request Forgery
SSRF via URL parameters, webhook targets, and import functionality.
Security Misconfiguration
CORS misconfiguration, verbose error messages, and insecure default settings.
Improper Inventory Management
Shadow API discovery, deprecated endpoint enumeration, and version confusion.
Unsafe Consumption of External APIs
Third-party API trust abuse and downstream data injection.
REST, GraphQL & SOAP
Each protocol has its own attack surface. Our testers apply protocol-specific sequences, not generic API checks.
- Endpoint enumeration
- HTTP verb tampering
- Parameter pollution
- Shadow API discovery
- CORS misconfiguration
- Introspection exposure
- Nested query DoS
- Batched mutation attacks
- Field-level authz bypass
- Schema enumeration
- WSDL enumeration
- Injection via SOAP envelope
- WS-Security bypass
- XML External Entity (XXE)
- Action spoofing
Automated tools find the obvious.
DAST scanners and automated security tools cannot understand business context, session state, or multi-user object relationships. These are the vulnerability classes that require a human analyst.
Engagement Workflow
Structured to minimise operational friction and maximise the value of the testing window.
Scoping & Documentation
We review your API documentation (Swagger/OpenAPI, Postman collections) to understand the endpoints and data models. Most API assessments cover 20-100 endpoints across 3-5 days of testing. Provide your OpenAPI specification or Postman collection and we scope precisely within 24 hours.
Discovery & Fuzzing
Enumerating all REST API endpoints, GraphQL schema fields, and SOAP operations, including undocumented or shadow APIs not present in the provided specification. We combine automated fuzzing with manual analysis to identify error handling weaknesses and unexpected data exposure before manual logic testing begins.
Manual Logic Testing
The core of the assessment. Our analysts manually probe every authorisation boundary, testing for BOLA across multi-tenant object hierarchies, horizontal and vertical privilege escalation, mass assignment in nested payloads, and multi-step business logic manipulation. These are precisely the vulnerability classes that automated DAST scanners cannot reliably detect.
Detailed Reporting & Debrief
A structured technical report with each finding documented at CVSS-rated severity, including reproduction steps and cURL commands. All findings are mapped to the OWASP API Security Top 10 (2023) categories and include prioritised remediation guidance. An executive summary is provided for non-technical stakeholders. A debrief call is included.
Close the Loop.
After the Test.
Your API security report identifies what is exploitable today. We feed those exact findings into our 24/7 Managed SOC and EdgeProtect attack surface management, building custom detection rules for your API surface and continuously monitoring your external perimeter for new exposures between annual tests.
Explore Defensive ServicesEdgeProtect ASM
Continuous attack surface monitoring of your API perimeter and external exposures.
24/7 SOC Monitoring
Custom detection rules tuned to the specific API vulnerabilities from your assessment.
Web App Testing
Pair with web application penetration testing for complete application security coverage.
SSO Assessment
Identity provider misconfiguration review for APIs using single sign-on authentication.
Full Penetration Testing Catalogue
Comprehensive penetration testing services tailored to your environment.
Internal Testing
Post-perimeter assessments targeting Active Directory, lateral movement, privilege escalation, and segmentation validation from inside your network.
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Frequently Asked Questions
Common questions about this service, methodologies, and deliverables.
API penetration testing is a security assessment specifically focused on Application Programming Interfaces (REST, GraphQL, SOAP), also referred to as an API security assessment. Unlike web app testing which includes the UI, API testing interacts directly with the backend logic. It focuses on authorisation flaws (BOLA), data exposure, and logic vulnerabilities that allow attackers to access data without using the frontend application.
Yes. Every API penetration testing report includes findings tagged to the relevant OWASP API Security Top 10 (2023) category, from API1:2023 Broken Object Level Authorisation through to API10:2023 Unsafe Consumption of APIs. This structure is designed to satisfy internal audit evidence requirements, client compliance questionnaires, and external certification assessments such as ISO 27001 and SOC 2.
Cost depends on the number of endpoints, authentication complexity, and environment type (external-facing product API, internal microservices, or a combination). Most engagements covering 20-100 endpoints are scoped across 3-5 days of testing. We provide a fixed-price quote within 24 hours of receiving your API specification or Postman collection. Contact us to discuss scope and we will respond the same working day.
Most API security assessments take 3-5 days of testing plus 1-2 days for report production. A final debrief call is included. Timelines vary with endpoint count and complexity. For urgent assessments ahead of product releases or compliance deadlines, we can discuss accelerated scheduling.
Yes. GraphQL APIs present unique security challenges including introspection data exposure, deep nesting denial of service, batched mutation attacks, and field-level authorisation bypass. Our methodology includes dedicated GraphQL-specific test cases alongside standard API security testing across REST and SOAP.
BOLA (Broken Object Level Authorisation) is the number one vulnerability in the OWASP API Security Top 10. It occurs when an API allows an authenticated user to access resources (such as invoices, messages, or profiles) belonging to other users simply by changing the ID in the request. We rigorously test every endpoint for BOLA across single and multi-tenant architectures.
Providing documentation (Swagger, OpenAPI, or Postman collections) allows for a much more comprehensive white-box test, ensuring full coverage of all endpoints. Without documentation (black-box), we can still test, but coverage may be limited to endpoints discovered through frontend analysis.
Yes. We can test internal microservices via VPN access or a testing appliance. Securing internal APIs is critical because if an attacker breaches the perimeter, lateral movement often relies on exploiting unprotected internal service-to-service communication.
A web app pen test focuses on the application as a whole, including browser-side security and the UI. An API pen test ignores the UI and focuses purely on data exchange and backend logic. For modern applications (single-page apps, mobile), API testing is often where the most critical vulnerabilities are found.