API Penetration Testing
Manual, researcher-led API pentesting covering REST, GraphQL, gRPC, and microservices
What this engagement covers
The service
Modern cloud architectures and mobile apps rely heavily on APIs, making them the primary entry point for targeted attacks. Our API penetration testing services go far beyond automated OpenAPI/Swagger scans. Senior offensive security researchers manually interrogate authentication mechanics, test authorization boundaries for BOLA/BFLA, manipulate parameter state, and execute chained multi-step attacks against your REST, GraphQL, and microservice APIs with zero false positives.
What we test
We thoroughly assess REST, GraphQL, gRPC, and SOAP APIs. Testing covers authentication mechanics (OAuth 2.0, JWT, API keys, mTLS), Broken Object Level Authorization (BOLA/IDOR), Broken Function Level Authorization (BFLA), mass assignment, rate-limit bypassing, SSRF through webhooks, unauthenticated schema introspection, and sensitive data exposure.
Scoping & Assessment Depth
Gray Box Testing (Recommended)
Most PopularAuthenticated testing across multiple API tokens and role tiers (Admin, Member, Read-Only) to test object-level and function-level access control.
Black Box Testing
Adversary SimulationUnauthenticated discovery and testing of public endpoints, hidden routes, undocumented parameters, and perimeter gateway rules.
White Box / Hybrid Testing
Maximum DepthComplete API specification, OpenAPI/Swagger files, Postman collections, and backend route code access for maximum architectural coverage.
Attack Surface & Vulnerability Vectors
Broken Object Level Authorization (BOLA)
Accessing other tenants' data or modifying arbitrary database records by altering endpoint object identifiers in API requests.
Broken Function Level Authorization (BFLA)
Invoking administrative, internal, or financial endpoints from low-privileged user tokens due to missing role enforcement.
Unrestricted Resource Consumption
Rate-limit evasion, GraphQL recursive depth attacks, batch query abuse, and payload size bypasses degrading system availability.
Mass Assignment & Parameter Tampering
Overwriting protected object attributes (e.g. role, permissions, credit balance) via unvalidated JSON/GraphQL request parameters.
SSRF & Webhook Callback Abuse
Forcing backend API servers to make unauthorized internal network requests or exfiltrate metadata via user-supplied webhook URLs.
Token Security & Signature Tampering
JWT signature manipulation (none algorithm, weak secrets), token leakage, lack of revocation, and OAuth redirect flow hijacking.
How we run it
Aligned with the OWASP API Security Top 10 (2023) and NIST SP 800-115, we deconstruct API contracts, analyze role permission matrices, and perform manual payload crafting to uncover logic flaws and privilege escalations that scanners miss. Every finding is validated with curl commands, JSON payloads, and remediation code snippets.
API Discovery & Attack Surface Footprinting
Mapping documented and undocumented endpoints, parameter schemas, shadow APIs, legacy versions (e.g. /v1 vs /v2), and developer consoles.
Authentication & Token Analysis
Inspecting OAuth 2.0 grant types, JWT claims, token lifespan, signature algorithms, session handling, and API key exposure risks.
Object-Level Authorization Testing (BOLA/IDOR)
Systematic cross-user and cross-tenant parameter fuzzing across GET, PUT, POST, and DELETE verbs to verify object ownership boundaries.
Function-Level Authorization Probing (BFLA)
Attempting administrative and management API function calls using regular user and anonymous tokens across administrative paths.
Business Logic & State Manipulation
Analyzing multi-step API transactions, payment confirmation flows, race conditions, coupon application, and workflow sequence bypasses.
Mass Assignment & Property Injection
Testing API model binding by injecting unexpected object fields into payload bodies to manipulate internal state variables.
Rate Limiting & Denial-of-Service Testing
Probing rate-limiting controls, batching endpoints, resource-heavy queries, and GraphQL query complexity limits under load.
Reporting & Retest Validation
Publishing verified findings with reproduction curl scripts, CVSS scores, remediation code examples, and verifying fixes with free retesting.
What you receive
Findings land in your tracker as you go, not only in a PDF at the end. Retest is in scope, not a change order.
- Executive summary with business impact and API risk posture analysis
- Technical vulnerability report with verified CVSS v3.1/v4 scores
- Working proof-of-concept (PoC) curl commands and JSON payload reproductions
- Step-by-step developer remediation guidance with code examples
- Auditor-ready compliance crosswalk (PCI-DSS 4.0, SOC 2, HIPAA, ISO 27001)
- Talon real-time portal access with bi-directional Jira/GitHub ticket sync
- Post-remediation retest report validating fixes before attestation
- Formal, signed Letter of Attestation for customers and security questionnaires
What we usually find
The issues this engagement surfaces most often. Yours will differ, but this is the shape of it.
Who this is for
Auditor-Ready Compliance Crosswalk
| Framework | Control Section | Testing Evidence & Report Deliverable |
|---|---|---|
| PCI DSS v4.0 | Requirement 11.4.3 & 6.4.1 | Penetration testing of application programming interfaces (APIs) exposing cardholder data or supporting payment infrastructure. |
| SOC 2 Type II | CC4.1, CC4.2, CC7.1 | Evidence of regular API intrusion testing and remediation tracking accepted by independent CPA firms for Trust Services Criteria. |
| HIPAA Security | 45 CFR § 164.308 | Technical evaluation of APIs transmitting or processing electronic Protected Health Information (ePHI) across health networks. |
| ISO/IEC 27001:2022 | Control A.8.8 & A.8.25 | Vulnerability management and secure development lifecycle validation for API-driven architectures and microservices. |
| FedRAMP / NIST | NIST SP 800-53 CA-8 | Formal penetration testing evidence for cloud service providers and federal API gateway integrations. |
Findings are mapped to OWASP API Top 10, PCI-DSS, HIPAA, SOC 2, ISO 27001, so the report drops into an audit package rather than needing to be translated first. If you need the readiness work behind one of those, that is a separate engagement.
Frequently Asked Questions
Direct answers on scoping, methodology, compliance validation, and deliverables.
We coordinate closely with your team before testing begins. When possible, testing is performed against a dedicated staging environment populated with realistic synthetic data. When testing in production is required, we use custom headers, non-destructive payloads, and dedicated test tenant accounts to avoid disrupting live customer operations.
An OpenAPI/Swagger specification, Postman collection, or API documentation is ideal and accelerates scoping. However, if complete documentation is unavailable, our researchers can perform black-box endpoint discovery and parameter reverse-engineering from web and mobile client network traffic.
Yes. We test REST, GraphQL, and gRPC endpoints. For GraphQL, we test for introspectable schemas, deeply nested query recursion, batching attacks, and field-level authorization bypasses. For gRPC, we assess protocol buffer definitions, serialization parsing, and service access control.
Yes. Every API penetration test includes complimentary retesting within 30 to 60 days. Once your engineering team applies the recommended code changes, our researchers re-execute the exact attack payloads to verify remediation and issue an updated clean attestation.
Active testing typically takes 1 to 2 weeks depending on the number of endpoints and role tiers. Critical vulnerabilities are published immediately to your Talon client portal during testing so developers can begin remediation without waiting for the final report.
Scope it in one call
Tell us what is in scope and we come back with a fixed price and a start date. No discovery-call maze, no hourly estimate that moves.
