API Penetration Testing Services

Your APIs are the back door, the side door, and most of your data. We test them the way attackers actually find and exploit them.

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APIs Are Where Modern Breaches Start

Every modern application is mostly API. Mobile clients, web frontends, partner integrations, microservices, internal tooling. Each one is a contract between systems, and most of the breach data over the last three years comes from those contracts being violated. Authorization that didn’t quite hold. An endpoint nobody documented. A token that worked when it shouldn’t have.

2025 API SECURITY THREAT DATA

SOURCES: VERIZON DBIR 2025, IBM COST OF A DATA BREACH 2025, Akamai’s 2024 API Security Impact Study

Breaches involving a web application vector60%

Average U.S. data breach cost$10.22M

Experienced an API security incident over the past 12 months84%

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Why API Testing Is Different from Web Application Testing

APIs don’t have a UI. There are no screens to click through, no forms with helpful validation messages, no visual hierarchy that tells a tester (or attacker) where to look. APIs are pure logic, pure data, and pure trust. Testing them well requires a different methodology and a different mindset.

No UI Means No Guardrails

Web apps fail loudly when something goes wrong. APIs fail quietly. A misrouted request, a missing authorization check, an over-permissive response, none of it surfaces visually. We test what the API actually returns, not what the documentation says it should.

Authorization Is the Whole Game

The most common API breach pattern is broken object-level authorization (BOLA). User A’s token works on User B’s data. Tenant 1 can read Tenant 2. Authenticated users access admin functions. We probe every endpoint at every privilege level to find the assumptions that don’t hold.

Preventing Financial Losses

A compromised API can lead to significant financial losses through data breaches, service disruptions, or regulatory fines. By identifying vulnerabilities early, penetration testing minimizes the risk of costly incidents and ensures your business operations remain uninterrupted.

Building Trust and Confidence

Securing your APIs demonstrates a commitment to protecting sensitive data and maintaining system integrity. This reassures customers, partners, and stakeholders that your organization prioritizes security, enhancing your reputation in the marketplace.

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API Types We Test

Every API architecture, every protocol, every authentication scheme.

REST/RESTful APIs

The most common API architecture. We test JSON and XML endpoints, HTTP method enforcement, OAuth and JWT handling, API key validation, parameter tampering, and the gap between REST conventions and what your specific implementation actually does.

GraphQL APIs

GraphQL’s flexibility is also its attack surface. We test introspection exposure, query depth and complexity attacks, batch query abuse, field-level authorization, alias-based rate limit bypasses, and GraphQL-specific injection patterns.

SOAP APIs

Enterprise and legacy systems often still depend on SOAP. We test XML-based vulnerabilities, WSDL exposure, WS-Security implementation flaws, XXE injection, and the integration boundaries where SOAP services connect to modern systems.

gRPC APIs

High-performance APIs using Protocol Buffers. We test service definitions, authentication interceptors, message validation, reflection exposure, and the gRPC-specific abuse patterns most security teams haven't seen yet.

WebSocket APIs

Real-time bidirectional channels. We test connection authentication and persistence, message injection, origin validation, and the assumptions WebSocket implementations make about what the connecting client is authorized to do.

Internal and Microservice APIs

APIs between your internal systems are routinely under-protected because "they're not exposed." Until they are. We test authentication boundaries, lateral movement opportunities, and the trust assumptions that fall apart when an attacker reaches your internal network.

Third-Party & Partner APIs

APIs that connect your systems to external partners, vendors, or customers. We test integration security, data exposure, authentication delegation, replay protection, and trust boundary failures that compromise both sides of the integration.

Mobile Backend APIs

The APIs your mobile applications depend on. We test client-side secrets that should never have been client-side, certificate pinning bypasses, offline authentication weaknesses, and the assumptions mobile backends make about request origins. (For full mobile application testing, see our Mobile Application Penetration Testing service.)

Webhook Endpoints

Callback URLs and event-driven function APIs (AWS Lambda, Azure Functions, Google Cloud Functions). Often overlooked, frequently exposed. We test for SSRF, replay attacks, signature validation gaps, and the cold-start authorization patterns that serverless architectures introduce.

OWASP API Security Top 10 Coverage

Every Raxis API engagement covers the full OWASP API Security Top 10:2023, the industry standard framework for API risk. Separate from the OWASP Top 10 for web applications because APIs have a fundamentally different attack surface.

Broken Object Level Authorization (BOLA)

The number one API risk. Endpoints that accept an object ID and return that object's data without verifying the requesting user is authorized to see it. We probe every endpoint that accepts an identifier (user ID, order ID, document ID, tenant ID) for cross-account and cross-tenant access.

Broken Authentication

Weak token generation, broken session management, password reset flaws, missing brute-force protection, and authentication endpoints that leak data through timing or response differences.

Broken Object Property Level Authorization (BOPLA)

APIs that return more fields than the user should see, or accept updates to fields the user shouldn't be able to modify (mass assignment). We map the full set of fields each endpoint exposes and accepts, then test which roles should have access to each.

Unrestricted Resource Consumption

Missing rate limits, missing query complexity limits, missing pagination caps, expensive operations exposed without throttling. We test what your API costs an attacker to abuse and what abuse looks like when it's economically feasible.

Broken Function Level Authorization

Admin endpoints accessible to standard users, internal-only functions reachable from external networks, privilege escalation through function access. We map every exposed function and test it at every privilege level.

Unrestricted Access to Sensitive Business Flows

APIs make business logic abuse cheap and fast. Coupon stacking, inventory manipulation, automated account creation, scalping, fraud at scale. We identify the business flows your API exposes and test the abuse patterns that target them.

Server Side Request Forgery (SSRF)

APIs that fetch URLs, process webhooks, or proxy external data are common SSRF vectors. We test for coerced requests to internal services, cloud metadata endpoints, and attacker-controlled destinations.

Security Misconfiguration

Verbose error messages, missing security headers, exposed debug endpoints, permissive CORS, default credentials, and the misconfigurations that compound into real attack paths.

Improper Inventory Management

Old API versions still routing traffic, deprecated endpoints that nobody monitors, staging environments accidentally exposed in production. We discover and test the APIs your team forgot about.

Unsafe Consumption of APIs

Your API is also someone else's third party. We test how your application validates and trusts data from upstream APIs, partner services, and integrated systems, where a compromise of an external party can cascade into your environment.

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How We Test

Methodology grounded in the OWASP API Security Top 10:2023 and the OWASP Web Security Testing Guide. Manual exploitation backed by AI-augmented reconnaissance. Every engagement adapts to your API surface, your tooling, and your release cadence.

Scoping and Discovery

We map your API surface from documentation, traffic capture, and reconnaissance. Swagger specs and Postman collections are the starting point, not the endpoint. We find what's documented, then we find what isn't. Hardcoded keys in public repositories, deprecated versions still answering requests, partner integrations that expose more than they should.

Authentication and Authorization Testing

We test token generation, session handling, MFA enrollment, and password recovery. Then we test authorization at every endpoint at every privilege level. BOLA, BOPLA, broken function-level authorization, and the cross-tenant boundary failures that destroy SaaS companies when they go public.

Input Validation and Injection Testing

SQL injection, NoSQL injection, command injection, and the API-specific patterns scanners miss. We test every parameter that accepts user input, every endpoint that processes untrusted data, and every place your API decides whether something is safe to use.

Business Logic and Abuse Testing

Rate limit bypasses, coupon stacking, inventory manipulation, automated account creation, scraping, and the business flow abuse that scanners can't reason about. We test what your API costs to abuse and what abuse looks like when it's economically rational for an attacker.

Real-Time Findings Through Raxis One

Critical and high-severity findings hit your Raxis One portal as we discover them, with proof-of-concept evidence, exploitation steps, and remediation guidance. Your team starts fixing while we keep testing.

Direct Engineer Access

Talk to the engineer testing your API. No ticket queues. Walk through findings on a call, validate scoping assumptions, ask questions in real time. The person hacking your API is the person you talk to.

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Comprehensive Role-Based Testing

Most API breaches happen at role boundaries. We test from every authentication state your API will encounter, from no token at all to full admin.

Unauthenticated

We test what your API exposes before authentication. Information disclosure, authentication bypass, mass enumeration through registration or password reset endpoints, and the public endpoints developers forgot existed.

Standard User

With a low-privilege token, we attempt operations that should be reserved for higher-privilege roles. Vertical privilege escalation, broken function-level authorization, IDOR on protected resources, and access to administrative endpoints by manipulating function names or parameters.

Administrative User

With full access, we map every endpoint your API exposes and test for the misconfigurations, debug interfaces, and internal functions that should never have been admin-accessible to begin with. We also look for what privileged tokens can do that they shouldn't, including modifications that would compromise the integrity of your data or systems.

Cross-Tenant (Multi-Customer SaaS)

For SaaS APIs, we validate that one tenant cannot read, modify, or impact another tenant's data through any path. Direct object references, shared resources, indirect channels, and the small permission gaps that compound into a full cross-tenant compromise.

Raxis Hack Stories

Our stories are based on real events encountered by Raxis engineers. Some details have been altered or omitted to protect customer identities.

How a Modified API Request Bypassed Role Controls and Exposed Internal Data

APIs are tricky to secure because, by design, they're meant to be open to requests from many directions. From internal company web and mobile applications to external API calls allowing vendors and customers to view and manipulate data, an API penetration test looks for any unintended opening.

Our pentester mapped out the API for a SaaS product and started using the API in unintended ways. He found a chat feature designed to let API users with specific entitlements query an AI endpoint for relevant answers.

Limited user roles were only supposed to chat with the API about publicly available information. They weren't supposed to reach internal data. Our pentester started looking for a way to bypass that boundary as a limited user. Manipulating the query request in Burp Repeater, he discovered that modifying the transaction type made the endpoint reply with sensitive internal data even when authenticated as a limited user. Using the proof of concept in his Raxis pentest report, the customer updated the endpoint to remove the bypass and protect sensitive data.

API Penetration Testing for Regulatory Compliance

API testing satisfies penetration testing requirements under most major frameworks. Raxis engagements produce audit-ready documentation through Raxis One, mapped to the specific control language each framework uses.

PCI DSS 4.0

Satisfies Requirement 6.5 (testing for application vulnerabilities, including APIs that handle cardholder data) and Requirement 11.4 (penetration testing). API endpoints that touch CHD or CDE infrastructure are explicitly in scope.

HIPAA Security Rule

Supports the technical evaluation requirement under §164.308(a)(8) for systems handling ePHI. APIs supporting patient portals, EHR integrations, and provider applications are in scope for healthcare organizations.

SOC 2

Provides auditor-ready evidence for Common Criteria CC4.1 (monitoring controls) and CC7.1 (vulnerability management). API testing is a standard expectation for SOC 2 Type II audits of SaaS providers.

GLBA Safeguards Rule

Supports the periodic penetration testing requirement for financial institutions. APIs handling NPI through customer portals, partner integrations, and core banking platforms are in scope.

ISO/IEC 27001:2022

Aligned with Annex A.8.29 (security testing in development and acceptance) and A.5.7 (threat intelligence informed testing). API security testing is increasingly expected as part of the broader application security control set.

GDPR Article 32

Article 32 requires "regular testing, assessing and evaluating the effectiveness of technical and organisational measures." API security testing is a standard implementation of that requirement for organizations processing EU personal data.

API Penetration Testing FAQ

API penetration testing focuses on the backend services, authentication, authorization, and business logic of your APIs, testing how they handle requests, process data, and enforce permissions. Web application testing covers the user interface, client-side code, and how users interact with your application through a browser. APIs often handle sensitive data and business-critical functions without the visibility of a UI, which makes them attractive targets. Most modern applications need both.

Yes. Undocumented APIs are often the most vulnerable because they receive less security scrutiny. We use traffic analysis, reverse engineering, and dynamic testing to discover and map undocumented endpoints, parameters, and functionality. We test REST, GraphQL, SOAP, gRPC, and custom protocols whether documentation exists or not.

Not when done properly. We craft requests carefully to avoid triggering rate limits, exhausting resources, or corrupting data. We work with your team to establish testing windows, throttle our request rate, and use dedicated test accounts when possible. For sensitive production environments, we can test against staging or development instances. We typically recommend at least some production testing because staging configurations often differ from production in ways that hide real-world vulnerabilities.

For authentication, we evaluate token generation, session management, password policies, MFA implementation, and credential transmission. For authorization, we test role-based access controls, privilege escalation paths, broken object-level authorization (BOLA, the #1 OWASP API risk), and broken function-level authorization. We create multiple test accounts at different privilege levels and systematically attempt to bypass authorization checks, access other users' data, and perform unauthorized operations.

Yes. We test APIs using your existing authentication mechanisms, including OAuth tokens, JWT, API keys, SAML assertions, and custom schemes. You can provide test credentials, or we can work with your team to generate them. We also test the security of the authentication mechanism itself, including weak token generation, insufficient validation, token leakage, and session management flaws.

Broken object-level authorization (BOLA), excessive data exposure, missing rate limits, injection flaws (SQL, NoSQL, command injection through API parameters), business logic abuse, mass assignment, security misconfigurations, and improper inventory management (old API versions still routing traffic alongside newer ones). These map directly to the OWASP API Security Top 10:2023.

Yes. GraphQL has unique security considerations, including introspection exposure that reveals your entire schema, query depth and complexity attacks that exhaust resources, batch query abuse, field-level authorization gaps, alias-based rate limit bypasses, and information leakage through field suggestions. Our team has extensive experience with GraphQL security and tests it as a distinct attack surface, not as a variation of REST.

A simple API with 10-20 endpoints typically takes one to two weeks. Mid-complexity APIs with 50+ endpoints, multiple authentication methods, and complex business logic typically take two to three weeks. Enterprise-scale API ecosystems with hundreds of endpoints, microservices, and extensive functionality can take three to six weeks or more. We provide a detailed timeline during scoping. For organizations with continuous deployment, we also offer ongoing API testing through Raxis Attack PTaaS.

At minimum, endpoint URLs, authentication credentials for test accounts, and ideally API documentation (Swagger or OpenAPI specs, Postman collections, or similar). Helpful additions include expected request and response formats, business logic workflows, role definitions, and any operations you want us to avoid. We can also test with minimal documentation, approaching your API the way an attacker would, to surface undocumented endpoints and functionality. Less information makes the simulation more realistic but extends the timeline.

Scoping starts with a 30-minute conversation. We need a rough sense of API count, endpoint count per API, authentication mechanisms, role complexity, and the business logic at stake. We can scope from documentation, from a brief technical walkthrough, or both. Most engagements move from scoping conversation to formal proposal within a few days. (If you'd rather skip ahead, request a quote and we'll come back with the questions we need answered.)

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Ready to Find What Your Scanner Can't?

Real engineers, real exploitation, real-time findings. Talk to a Raxis penetration tester about scoping an API engagement that fits your architecture, your release cadence, and the business logic at stake.

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