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Estimation errors eliminated for a construction firm

Redesigned the field team's daily workflow from the ground up.

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Post-sales chaos resolved for an EV manufacturer

Six structural breakdowns, one root cause.

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API Pentesting Service

Secure your APIs before cyber attackers find the gaps.

We at Nimblechapps are committed to securing your APIs with end-to-end pentesting across REST, SOAP, GraphQL, gRPC, WebSockets, and event-driven architectures. We uncover the authentication, authorization, business-logic, and data-exposure threats looming on your APIs and counter them with our expert security testing team.

Free Consultation
Types of API Pentesting

End-to-end coverage across every major API architecture.

From REST and SOAP to GraphQL and WebSockets, our team validates real-world attack paths against the interfaces that power your products.

REST API pentesting
We provide API pentesting for the most common API architecture i.e. REST APIs. Our REST API pentesting focuses on identifying unused endpoints that may expose sensitive data, preventing unauthorized access, preventing attackers from manipulating server-side queries, reducing risk of leaking PII, and protecting data integrity and confidentiality during transmission.
SOAP API pentesting
Through SOAP API pentesting service we focus on finding and exploiting security vulnerabilities in APIs that use the Simple Object Access Protocol. We identify exposed API structures, methods, and schemas, weak authentication or token handling, unexpected data and logic abuse, poorly validated headers, and crashes.
GraphQL API pentesting
Through GraphQL API pentesting we identify the security flaws unique to GraphQL’s query model. Our team of experts focuses on schema introspection, testing each resolver, checking sensitive data fields, testing input values for SQL/NoSQL injection, and much more.
WebSocket pentesting
Our team stresses on securing real-time, bidirectional communication channels between the client and the server. Through WebSocket, pentesting services tend to verify the handshake authentication, test for message tampering, testing payloads for injection flaws, and more.
Why API Pentesting?

API pentesting is a necessity, not a nice-to-have.

Modern apps live and die by their APIs. Pentesting ensures the powerful functions you expose to the internet aren’t the same ones an attacker uses against you.

Internet-Exposed Functions
Microservices, mobile backends, and partner integrations often expose powerful functions directly to the internet, making them prone to cyber attacks. API pentesting is a must for all the aspects of an app.
Prevent Data Leaks
API pentesting finds excess data exposure, IDOR/BOLA, mass assignment, and weak pagination/filters that leak PII or sensitive records - ensuring no data leaks are made.
Token & Role Hardening
Pentesting ensures tokens (JWT, opaque), scopes, and roles can’t be abused or escalated by attackers attempting privilege escalation against your APIs.
Real-World Attack Simulation
API pentesting evaluates the resilience of an API against real-world attacks, covering data security in transit, authentication, authorization, input validation, business logic, and configuration issues.
OWASP API Top 10 Alignment
We align tests to the OWASP API Security Top 10, modern identity standards, and your specific business logic to deliver an assessment that maps to known industry threat models.
Compliance Readiness
Regular API security testing helps you meet compliance mandates and maintain stakeholder confidence by demonstrating a proactive posture against API-borne threats.
Skilled API Pentesting Experts
At Nimblechapps, we bring together a team of highly skilled API penetration testing experts with deep expertise in secure coding practices, modern API security frameworks, and industry best practices. Our team has hands-on experience performing in-depth security assessments for REST, SOAP, GraphQL, gRPC, WebSockets, and event-driven APIs across diverse industries, platforms, and technology stacks.
Custom API Pentesting Approach
Our API penetration testing methodology is fully customizable - whether you require black-box testing for public-facing APIs, gray-box testing with limited access, or white-box testing with full documentation and credentials. We tailor our approach to align with your specific risk profile, compliance mandates, and API architecture.
Flexible Hiring Model
Nimblechapps offers flexible engagement models to fit your operational needs. Whether you need a one-time API security audit before deployment, scheduled quarterly assessments for ongoing compliance, or a dedicated security partner for continuous monitoring and threat mitigation, we adapt to your requirements.
Cost Efficiency
Our API penetration testing services are designed to deliver maximum security impact without the premium price tag of traditional security firms. We combine open-source and commercial testing tools, automate repetitive tasks, and streamline our reporting process to ensure cost-effective, efficient, and thorough assessments.
Ongoing Maintenance & Support
At Nimblechapps, we go beyond simply reporting vulnerabilities. We collaborate with your development and DevSecOps teams to provide actionable remediation guidance, perform post-fix re-testing, and offer ongoing monitoring and consulting to ensure your APIs remain secure against evolving threats.
OWASP-Aligned Methodology
Every engagement is anchored to the OWASP API Security Top 10 and modern identity standards, with attention to your business logic. Get a quote for a tailored assessment.
Our Tech Stack

The tools and standards we test with.

OWASP ZAP
Postman
SwaggerHub
ReadyAPI
GraphQL Voyager
REST
SOAP
GraphQL
How We Work

A structured, five-step API pentesting engagement.

Anchored to the OWASP API Security Top 10 and tailored to your business logic — from scoping to re-testing, we make every engagement count.

01

Scoping & Reconnaissance

We begin with a deep-dive into your API estate - endpoints, schemas, authentication flows, and downstream dependencies. We map the attack surface across REST, SOAP, GraphQL, gRPC, and WebSocket interfaces and align scope to your risk profile and compliance mandates.

02

Threat Modelling

Using the OWASP API Security Top 10 as a baseline, we build a threat model tailored to your business logic. We identify trust boundaries, authorization paths, and high-value data flows that warrant focused testing during the engagement.

03

Active Pentesting

Our experts run black-box, gray-box, or white-box assessments depending on the engagement. We probe for broken object level authorization, mass assignment, token misuse, rate-limit bypass, injection flaws, and business-logic abuse using a blend of manual testing and tooling.

04

Reporting & Remediation Guidance

You receive a detailed, prioritized report with reproduction steps, business impact, and concrete remediation guidance. We work directly with your development and DevSecOps teams to ensure findings are understood and actionable.

05

Re-testing & Continuous Support

Once fixes are deployed, we re-test the affected endpoints to verify remediation. We also offer ongoing monitoring and consulting so your APIs stay resilient against evolving threats long after the initial engagement.

FAQs

Frequently Asked Questions.

What is API Penetration Testing?
API Penetration Testing is a controlled security assessment of the application programming interfaces or API to identify vulnerabilities in design, implementation, and deployment. Unlike a generic web app security testing, API pentesting targets machine-to-machine interfaces (mobile, web, microservices, partner integrations) and validates real-world attack paths - from broken object level authorization to mass assignment, from token misuse to rate-limit bypass.

API pentesting evaluates the resilience of an API against real-world attacks, covering data security in transit, authentication, authorization, input validation, business logic, and configuration issues. We align tests to OWASP API Security Top 10, modern identity standards, and the business logic.
Why is API pentesting a necessity?
With the mobile and web applications relying heavily on the APIs to perform, API pentesting has become a necessity rather than a nice-to-have functionality. Various reasons suggest that API pentesting is needed for the applications to ensure security.
  • Microservices, mobile backends, and partner integrations often expose powerful functions directly to the internet making them prone to cyber attacks. Hence, API pentesting is a must for all the aspects of an app.
  • API pentesting finds excess data exposure, IDOR/BOLA, mass assignment, and weak pagination/filters that leak PII or sensitive records. Thus, ensuring no data leaks are made.
  • API pentesting ensures tokens (JWT, opaque), scopes, and roles can’t be abused or escalated.
Which API architectures do you test?
We perform end-to-end pentesting across the most widely deployed API architectures:
  • REST APIs - identifying unused endpoints, unauthorized access, server-side query manipulation, and PII leakage risks.
  • SOAP APIs - uncovering exposed structures, weak authentication, header validation issues, and logic abuse.
  • GraphQL APIs - schema introspection, resolver-level testing, and SQL/NoSQL injection through input values.
  • WebSockets - handshake authentication, message tampering, and payload-level injection flaws.
  • gRPC and event-driven APIs - covered as part of the broader engagement scope.
What is your API pentesting methodology?
Our API penetration testing methodology is fully customizable - whether you require black-box testing for public-facing APIs, gray-box testing with limited access, or white-box testing with full documentation and credentials. We tailor our approach to align with your specific risk profile, compliance mandates, and API architecture, anchored to the OWASP API Security Top 10 and modern identity standards.

Interested? Book a free consultation.
Do you offer remediation guidance and re-testing?
Yes. We go beyond simply reporting vulnerabilities. We collaborate with your development and DevSecOps teams to provide actionable remediation guidance, perform post-fix re-testing to validate the fixes, and offer ongoing monitoring and consulting to ensure your APIs remain secure against evolving threats.
What engagement models do you offer?
Nimblechapps offers flexible engagement models to fit your operational needs:
  • One-time API security audit before deployment.
  • Scheduled quarterly assessments for ongoing compliance.
  • A dedicated security partner for continuous monitoring and threat mitigation.

Reach out to discuss the model that fits you best.
How do you keep API pentesting cost-efficient?
Our API penetration testing services are designed to deliver maximum security impact without the premium price tag of traditional security firms. We combine open-source and commercial testing tools, automate repetitive tasks, and streamline our reporting process to ensure cost-effective, efficient, and thorough assessments.
Will Nimblechapps sign a Non Disclosure Agreement to protect my project?
Yes, here is the Signed NDA. Nimblechapps has always shown full readiness to safeguard client information not only during the engagement but post-engagement as well.
Nimblechapps · Strategy First. Technology Always.

Let’s discuss your API pentesting needs today.

Nimblechapps is an experienced security partner that you can count on to deliver quality results quickly. Reach out for a free consultation and a security evaluation of your APIs - we’ll get back to you within 24 hours.

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