Service Overview

APIs now carry the majority of business logic and sensitive data flow in modern applications, yet they often receive less security scrutiny than the UI surfaces they back. Broken object-level authorisation, mass assignment, excessive data exposure, and missing rate limiting consistently top the OWASP API Security Top 10 because they remain genuinely prevalent.

Just Hacked On delivers specialised API penetration testing across REST, GraphQL, SOAP, and gRPC interfaces. Our testers approach APIs with the depth they deserve: manual authorisation matrix testing across roles, business logic exploration, rate limiting and abuse testing, and mass assignment hunting.

Every engagement combines automated tooling for surface coverage with senior manual testing on the issues automation systematically misses.

Logic Flaw Hunting

Auth & JWT Testing

BOLA / IDOR Discovery

Developer-Ready Fixes

Secure Your Endpoints

Provide your Swagger/OpenAPI docs or Postman collections — the JHO desk will respond with a tailored proposal and engagement plan.

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SLA: RESPONSE UNDER 24 HOURS

What is API penetration testing?

API penetration testing is a highly targeted, manual adversary simulation against your endpoint infrastructure. Modern APIs leverage diverse protocols (REST, GraphQL, SOAP, gRPC) and authentication mechanisms (OAuth 2.0, JWT, API keys), each presenting unique attack vectors that automated scanners consistently miss.

We map our attacks directly against the OWASP API Security Top 10, prioritizing critical vulnerabilities like Broken Object Level Authorization (BOLA), mass assignment, unrestricted resource consumption, and severe business logic flaws that lead to full data compromise.

What API testing delivers:

OWASP API Security Top 10 coverage across all endpoints

Authorisation matrix testing across roles and objects

Mass assignment and excessive data exposure identification

Rate limiting and abuse vector testing

Authentication and token handling validation

Business logic testing for API workflows

API testing has become as critical as traditional web application testing, particularly for organizations whose endpoints power mobile applications, B2B integrations, and microservice architectures.

Why API security testing matters

APIs now represent the primary attack surface for modern organizations. Single-page applications, mobile backends, and microservices expose significantly more attack vectors than traditional web interfaces. Developers often implement weaker authorization logic on backend endpoints, operating on the flawed assumption that "attackers won't find the direct API calls." At Just Hacked On, we know they will.

Major breaches in recent years trace directly back to API-level vulnerabilities: BOLA exposing millions of customer records, mass assignment allowing instant privilege escalation, and unrestricted endpoints enabling credential stuffing at scale.

Common consequences of weak API security:

Customer record exposure via BOLA in mobile/SPA backends

Privilege escalation via mass assignment in admin APIs

Credential stuffing at scale due to weak rate limiting

Sensitive data exposure via verbose API responses

Account takeover via authentication weaknesses

Compliance failures across PCI DSS and SOC 2

APIs deserve at least the same offensive testing depth as the UI surfaces they support—often more, given they typically lack robust authorization enforcement.

Industries We Serve

We deliver this service across these sectors:

Defence & Government

Financial Services

Healthcare

SaaS & Technology

Cloud Services

E-commerce & Retail

Education

Professional Services

OPERATIONAL FLOW

Our API Testing Methodology

Intelligence-led methodology combining OWASP API Security Top 10 with hands-on protocol-specific testing across REST, GraphQL, SOAP, and gRPC.

Scoping & API Documentation Review

We agree the in-scope API endpoints (typically working from OpenAPI/Swagger, GraphQL schema, or Postman collections), user roles, authentication schemes, and test credentials.

Endpoint Enumeration & Mapping

Complete mapping of every endpoint, method, parameter, and response shape, building the full attack surface before testing begins.

Authentication & Token Testing

Detailed testing of authentication mechanisms. JWT validation, OAuth flow integrity, token refresh logic, session fixation, and brute force resistance.

Authorisation Matrix Testing

Systematic testing of object-level and function-level authorisation across every user role pair, the highest-value work in any API engagement.

Mass Assignment & Data Exposure

Testing for mass assignment (unintended property writes), excessive data exposure (verbose responses leaking sensitive data), and improper input filtering.

Rate Limiting & Abuse Testing

Testing of rate limiting, account lockout, and abuse vectors that enable credential stuffing or data scraping at scale.

Business Logic & Workflow Testing

Manual exploration of business workflows for parameter tampering, race conditions, and logic flaws that automated tools cannot find.

Reporting & Developer Walk-Through

Detailed findings with reproduction steps via curl/Postman, code-level remediation guidance, and live walk-through with your engineering team.

Typical engagement: 5-10 days for mid-complexity APIs (under 50 endpoints), 10-15 days for larger APIs (50-150 endpoints), longer for major platforms.

ENGAGEMENT DELIVERABLES

What you receive

Every API penetration testing engagement with Just Hacked On includes:

Comprehensive scoping document paired with a full API endpoint and attack surface inventory

Board-ready executive summary translating technical API risks into clear business impact

Deep-dive technical findings featuring verifiable Proof-of-Concept (PoC) steps via cURL and Postman

Vulnerability prioritization combining standard CVSS scoring with real-world exploitability context

Actionable, code-level remediation guidance supported by secure configuration examples

Extensive authorisation matrix detailing test coverage across all user roles and privilege levels

Direct compliance mapping against the OWASP API Security Top 10 and major industry frameworks

Complimentary verification retest to ensure critical and high-severity logic flaws are permanently sealed

QUESTIONS & ANSWERS

API Pentesting, Answered

Clear answers to common questions about scoping, execution, and deliverables.

Ideally, we need API documentation (Swagger, OpenAPI, or GraphQL schema) or a populated Postman collection. We also need to know the total number of endpoints and the types of user roles (e.g., admin, standard user, unauthenticated) to provide an accurate fixed-fee quote.

Yes. Our senior consultants are highly experienced in testing modern REST APIs, complex GraphQL implementations (including introspection and query batching attacks), and legacy SOAP web services.

Automated tools can catch basic misconfigurations, but they cannot comprehend business logic or multi-step authorization checks. Our manual testing specifically targets complex vulnerabilities like Broken Object Level Authorization (BOLA/IDOR) and logic bypasses, which scanners consistently miss.

Yes, for a comprehensive test, we perform grey-box testing. We require credentials for at least two different users per role level. This allows us to thoroughly test for horizontal and vertical privilege escalation across your endpoints.

Yes. Every engagement includes a verification retest. Once your engineering team patches the reported API vulnerabilities, we re-evaluate those specific findings and issue an updated report proving they are safely closed.

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API Penetration Testing