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Offensive Security

API Penetration Testing

REST, GraphQL and gRPC testing focused on authorisation and data exposure.

Assessment of REST, GraphQL, SOAP and gRPC interfaces against the OWASP API Security Top 10, with emphasis on object and function level authorisation.

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Typical timeline
Typically 1–2 weeks depending on endpoint count
Business benefit
Close the authorisation gaps that expose data at machine speed and scale.
Industries
Banking & Financial ServicesHealthcareE-CommerceIT & Cloud ServicesGovernmentManufacturing

Overview

What API Penetration Testing covers

APIs are the most directly reachable part of a modern platform, and the least protected by the user interface. We test them as independent attack surface, not as a byproduct of the app.

Object-level authorisation, mass assignment, rate abuse and excessive data exposure receive dedicated, systematic coverage.

The problem we solve

API endpoints frequently trust identifiers supplied by the caller. One missing authorisation check can expose an entire customer database through a single enumerable parameter.

Scope & outcomes

What we test and what you receive

Scope coverage

  • Broken object level authorisation (BOLA/IDOR)
  • Broken function level authorisation
  • Authentication, token and key handling
  • Excessive data exposure and verbose errors
  • Mass assignment and parameter pollution
  • Rate limiting and resource consumption abuse
  • GraphQL introspection, depth and batching abuse
  • Schema, versioning and shadow endpoint discovery

Key benefits

  • Prevention of large-scale data exposure
  • Verified tenant and object isolation
  • Documented API security posture for partners
  • Reusable authorisation test cases for your pipeline

Deliverables

  • Executive summary written for business stakeholders
  • Technical findings with severity, CVSS and reproduction steps
  • Evidence: requests, responses, screenshots and payloads
  • Prioritised remediation roadmap
  • Remediation support session with your engineers
  • Re-test report and closure statement

Methodology

Our assessment process

  1. 01

    Scoping and rules of engagement

  2. 02

    Reconnaissance and asset mapping

  3. 03

    Threat modeling against business context

  4. 04

    Automated scanning and coverage checks

  5. 05

    Manual exploitation and chained attack paths

  6. 06

    Impact validation and evidence capture

  7. 07

    Risk analysis and prioritisation

  8. 08

    Reporting, debrief and remediation support

  9. 09

    Re-testing of fixed findings

Tooling

Tools and techniques

Tooling supports expert manual testing — it never replaces it.

Specification-driven endpoint enumeration
Custom authorisation matrix scripting
GraphQL introspection and query abuse tooling
Proxy-based fuzzing harnesses

FAQ

API Penetration Testing questions

An OpenAPI/GraphQL schema or Postman collection, endpoint documentation and credentials for at least two accounts per role.

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Ready to scope API Penetration Testing?

Talk to our offensive security team about scoping an assessment around your actual risk, stack and timelines.

Book a Security AssessmentTalk to a Security Expert

Prefer email? business@securityloyals.com