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Invadel

Application

API Penetration
Testing Services

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Senior certified testers, manual-first185+ years combined experienceOnboarding within 24 hoursFree retest includedOur methodology

When you need it

When you need API penetration testing services

The situations that bring teams to this engagement, and where it fits alongside the rest of your program.

  • You are launching a public API, opening partner integrations, or publishing an OpenAPI spec that attackers can read too.
  • A mobile or single-page app depends on the API, so the API is the real attack surface. Pair it with mobile application testing.
  • You run a multi-tenant SaaS platform and need proof one tenant cannot reach another’s data. See our SaaS testing guide.
  • The API is inside your SOC 2 or PCI DSS scope and the auditor expects application-layer testing evidence.
  • A bug-bounty report or incident involved an authorization flaw and you want the rest of the API checked the same way.
  • You release several times a week and want each major version tested without starting the scoping over. See our testing program.

Definition

What is API penetration testing?

API penetration testing is a manual attack on the endpoints behind your web and mobile apps. A tester calls every endpoint as each role and tenant, swaps object IDs, replays and tampers with tokens, and abuses business flows to prove which flaws are exploitable. It is the deepest form of API security testing, because scanners cannot tell which user should own which record.

Every API test here is a fixed price, from $4,000 for a small API, with a free retest of what you fix. The steps we follow are in our API penetration testing checklist and methodology, and the tiers are on the API testing price page.

What we look for

API vulnerabilities we hunt for

Testing covers all ten categories of the OWASP API Security Top 10 (2023) plus real attacker behavior, with the weight on the authorization and data-exposure flaws that dominate real-world API breaches.

Object & Function Authorization (API1, API5)

Endpoints that return or change objects without confirming the caller owns them, and admin functions reachable with an ordinary token. Together, the leading cause of API breaches.

We test for

  • Broken object level authorization (BOLA / IDOR)
  • Cross-tenant and cross-account access
  • Broken function level authorization (BFLA)
  • HTTP method and path-based bypasses
  • Predictable or enumerable identifiers

Authentication & Tokens (API2)

Weak token issuance, validation, or session handling that lets attackers impersonate users or services.

We test for

  • JWT signature, algorithm, and claim flaws
  • Token expiry, revocation, and refresh handling
  • OAuth 2.0 and OpenID Connect flow weaknesses
  • API key and secret handling
  • Credential stuffing and password-reset abuse

Property-Level Authorization & Data Exposure (API3)

APIs that return more data than a client needs, or accept fields they should never trust.

We test for

  • Over-broad response objects
  • Mass assignment of protected fields
  • Sensitive data in responses and errors
  • Field-level authorization, including GraphQL fields

Resource Consumption & Business Flows (API4, API6)

Missing limits that turn ordinary features into brute force, scraping, and denial-of-service tools.

We test for

  • Unbounded requests, pagination, and payload sizes
  • Expensive and deeply nested queries
  • Brute-force and enumeration without throttling
  • Automated abuse of checkout, OTP, referral, and signup flows

SSRF, Injection & Misconfiguration (API7, API8)

Server-side flaws and insecure defaults that give an attacker a path into backend systems.

We test for

  • Server-side request forgery via URL parameters and webhooks
  • SQL, NoSQL, and command injection
  • CORS, TLS, and security header misconfiguration
  • Verbose errors, debug endpoints, and default credentials

Inventory & Third-Party APIs (API9, API10)

The endpoints nobody remembers and the upstream services everybody trusts.

We test for

  • Shadow, legacy, and deprecated API versions
  • Undocumented endpoints and staging exposures
  • Unsafe consumption of third-party API responses
  • Webhook signature and origin validation

API types

REST, GraphQL, and SOAP: what changes in testing

The OWASP categories apply to every API style, but the techniques do not. Each type gets its own test plan.

REST

The most common target. Testing concentrates on object and function authorization across every method and path, token handling, mass assignment through JSON bodies, and the version sprawl (v1, v2, internal) that leaves old endpoints alive.

GraphQL

A single endpoint with an enormous surface. We test introspection exposure, field- and object-level authorization on nested queries, batching and aliasing abuse that defeats rate limits, query-depth and complexity attacks, and injection through resolvers. Our guide to GraphQL security testing shows each attack and its fix.

SOAP

Still common in finance, insurance, and healthcare integrations. We test WS-Security and signature handling, XML external entity (XXE) injection through the envelope, WSDL exposure, and legacy authentication schemes that predate modern controls.

Scoping

How we scope and test an API

What we need from you

  • An OpenAPI/Swagger specification or a Postman collection, or the documentation your developers use
  • A test account for each role and tenant, including at least two of each where cross-tenant testing matters
  • A staging environment where one exists, and rules of engagement for production where it does not

How we test

  • Burp Suite Professional, Postman, and purpose-built scripts for authorization and enumeration testing
  • Manual, role-by-role authorization testing of every endpoint, the work scanners cannot do
  • Methodology aligned to the OWASP API Security Top 10 and PTES

What you get back

  • A full inventory of the endpoints tested, so the auditor can see coverage
  • Findings with example requests and responses your developers can replay
  • A free retest of remediated findings, with the report updated to show them closed

Methodology

How we test

Full methodology →

Every engagement follows the Penetration Testing Execution Standard and the relevant OWASP guides.

These are the phases your API penetration testing runs through.

  1. 01

    Scope & threat model

    Roles, tenants, data flows, and the abuse cases that matter most to your business.

  2. 02

    Recon & mapping

    Every endpoint, parameter, and integration enumerated before a single payload is sent.

  3. 03

    Manual exploitation

    OWASP-guided manual testing with targeted tooling, chaining findings into real attack paths.

  4. 04

    Impact validation

    Each finding proven exploitable and rated by what an attacker could actually reach.

  5. 05

    Report & retest

    Executive and technical reports, then a free retest once your fixes ship.

How it works

How your engagement runs

From scope through the final retest, your team stays in the loop at every step, with findings tracked live in our platform.

  1. 01

    Scope & kickoff

    Targets, roles, and rules of engagement defined in writing, with a fixed scope and timeline.

  2. 02

    Testing goes live

    Findings post to your live platform dashboard the moment our testers confirm them.

  3. 03

    Track remediation

    Follow every finding from open to fixed, with severity, evidence, and status in one place.

  4. 04

    Report & retest

    Executive and technical reports land, then request a free retest in one click.

Compliance

Compliance frameworks this test satisfies

Findings are mapped to the requirement or control they evidence, so the same report serves your auditor, your customers, and your engineers.

SOC 2Evidence for CC6.1 logical access and CC7.1 vulnerability identification across the APIs inside your audit boundary.PCI DSSApplication-layer testing of payment APIs under Requirement 11.4, including the APIs that handle cardholder data.HIPAATechnical safeguard evidence for APIs that transmit ePHI between applications, devices, and partners.ISO 27001Annex A 8.8 and A 8.29 evidence for the APIs inside your ISMS scope.GDPRArticle 32 testing of the interfaces that expose EU personal data.
Common inFintechHealthcare & MedTechSaaS & SoftwareE-commerce & RetailInsuranceMedia & AdTechStartupsLogistics & TransportationAll industries

Proof

Proof in the field

Every engagement is confidential, so the work below is anonymized to sector and engagement type.

All case studies →

Free

Retest on every penetration test

185+

Years combined experience

14

Senior in-house specialists

24h

Onboarding after signing

Fintech · Payments

Web Application Penetration Test

High risk

Critical: a remote code execution flaw in the application’s web framework that could have given an attacker full control of the server. We escalated it to the development team while the test was still running.

Outcome. The critical RCE was reported and remediated during the engagement via an emergency framework upgrade, which also closed the server-side request forgery, and the remaining findings were retested to confirmation.

1

Critical (RCE)

Mid-test

Critical remediated

2

High

Read the case study

Fintech · Payments

Post-Incident Web App Assessment

Medium risk

Excessive data exposure: API responses leaked transaction metadata, including precise geolocation, enabling real-world tracking of users.

Outcome. Surfaced the exposure and hardening gaps, prioritized by how readily an attacker could chain them, and delivered fixes plus a retest to confirm closure.

8

Findings

3

Medium

Post-incident

Engagement

Read the case study
LatentPerygeeCity National BankAubaDesteiaDTCC
Request a reference 

Resources

Field notes from the offensive side

All articles →

The OWASP API Security Top 10, Explained

The OWASP API Security Top 10 names the risks that break real APIs. Here is what each category means in plain terms, and why authorization dominates the list.

API Penetration Testing: Methodology and Checklist

A step-by-step API penetration testing checklist for REST and GraphQL: the OWASP API Top 10 flaws that matter, how to test authorization, and how to scope it.

GraphQL Security Testing: Introspection, Batching and Authorization Flaws

GraphQL security testing explained: finding endpoints, introspection and suggestions, IDOR, batching and alias abuse, DoS, CSRF, and how to test each.

Want to see a report first?

Read a sample report for a fictional client, or request a redacted one from a real engagement. Our guide explains what a penetration testing report should contain.

See the sample report

FAQ

Frequently asked questions

What teams most often ask before scoping API penetration testing services.

Still have questions? 
01How is an API penetration test different from a web application test?

A web application test looks at the full application including its interface and logic, while an API test focuses on the backend endpoints, how they authorize requests, and how they expose data. Many teams run both, since modern applications depend heavily on APIs that attackers target directly.

02Is API security testing the same as an API penetration test?

API security testing covers any check of how secure an API is, including automated scanning and schema validation. An API penetration test is the manual, attacker-driven form of it: our testers authenticate as different roles and tenants, tamper with object identifiers, and abuse business flows to prove which issues are actually exploitable. Automated scanners consistently miss authorization flaws such as broken object level authorization, the top API risk, which is why manual testing matters.

03Which API types do you test?

We test REST, GraphQL, and SOAP APIs, whether they are public, partner-facing, or internal. Testing is aligned to the OWASP API Security Top 10 and tailored to how your API authenticates and handles data.

04How long does an API penetration test take?

Most engagements run about one week depending on the number of endpoints and their complexity, followed by reporting and a complimentary retest of any remediated findings.

05How is an API penetration test scoped?

Scope is based on the number of endpoints, the authentication models in play, and how many distinct roles or tenants need to be exercised. Share your API documentation or an OpenAPI spec during scoping and we will confirm coverage and a fixed price before testing begins.

06How much does an API penetration test cost?

API penetration tests start at $4,000 for a small API, fixed before work begins, with a free retest of remediated findings included. Larger APIs with many endpoints or complex role models are quoted after scoping. Starting prices for every service are on our pricing page.

07What is BOLA, and why does it matter so much for APIs?

Broken object level authorization (BOLA), also called IDOR in web applications, is when an API returns or modifies a record because the caller asked for it by ID, without checking that the caller is allowed to see that record. Change the invoice number in a request and get someone else’s invoice. It ranks first in the OWASP API Security Top 10 because it is common, trivial to exploit, and invisible to scanners, which cannot know which user should own which object. Every API test we run exercises it across every role and tenant.

08Can you test internal or partner APIs that sit behind authentication?

Yes. Most of the APIs we test are not public. We test from the position of an authenticated user, a partner integration, or a compromised client, using the credentials and network access you provide. Internal APIs are frequently the weakest, because teams assume the network boundary protects them.

Ready to test your defenses?

Talk to our team about scoping API penetration testing services.

Prefer the full scoping questionnaire? 
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