API and Microservices Penetration Testing

We test the security of REST, GraphQL, and other APIs by simulating real-world cyberattacks. API penetration testing helps identify vulnerabilities in authentication, authorization, OAuth, JWT, API gateways, input validation, and communication between microservices before attackers can exploit them. Our certified ethical hackers perform API security testing in line with the OWASP API Security Top 10, manually verifying each finding and providing proof of exploitability and clear recommendations for remediation.

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API and Microservices Penetration Testing

Why Test APIs and Microservices?

APIs connect web applications, mobile applications, cloud services, and third-party systems. They transmit sensitive data, execute business operations, and expose functionality that is critical to an organization. Vulnerabilities in authentication, authorization, or input validation can allow attackers to gain unauthorized access to data, bypass security controls, or compromise the entire application environment. API penetration testing simulates real-world attack scenarios and verifies whether identified vulnerabilities can actually be exploited. Our ethical hackers combine automated tools with manual testing based on the OWASP API Security Top 10. The result is not just a list of findings, but verified vulnerabilities supported by proof of exploitability and specific recommendations for remediation. Regular API penetration testing helps organizations protect sensitive data, secure communication between applications and microservices, and support compliance with standards and regulations such as NIS2, DORA, ISO 27001, and PCI DSS.

Protection of Sensitive Data

We verify whether APIs properly protect personal data, business information, authentication tokens, API keys, and other sensitive data.

Prevention of Unauthorized Access

We identify vulnerabilities that could allow attackers to access functions or data without the required permissions.

Support for Compliance with Security Standards

Penetration testing results support compliance with the requirements of NIS2, DORA, ISO 27001, PCI DSS, and other security standards.

Stronger Application Ecosystem Security

Regular API penetration testing helps identify weaknesses in communication between applications and microservices and improves the resilience of the entire environment against cyberattacks.

What We Test

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REST APIs

We test REST API security, including authentication, authorization, input validation, session management, and protection against unauthorized access.

GraphQL APIs

We assess GraphQL API security, including introspection, excessive data exposure, authorization, and protection against query abuse.

Authentication and Authorization

We test the implementation of OAuth, OpenID Connect, JWT tokens, API keys, and other access control mechanisms.

Input Validation

We test how APIs process input data and assess their resilience against SQL Injection, NoSQL Injection, Command Injection, and other attacks.

Microservices

We assess the security of communication between microservices, including identity and access management and trust between individual services.

API Gateway

We test API Gateway configuration, access control rules, rate limiting, logging, and other security mechanisms.

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What API Penetration Testing Can Reveal

API penetration testing goes beyond identifying individual technical vulnerabilities. It also assesses how multiple vulnerabilities can be combined to gain unauthorized access to sensitive data, bypass security controls, or compromise communication between services. Common findings include:

We verify whether manipulating object identifiers can provide unauthorized access to other users’ data or resources.

We test login mechanisms, API tokens, OAuth, JWT, and other authentication controls that, if compromised, could lead to account takeover.

We verify whether users can access API functions for which they do not have the required permissions.

We assess whether APIs expose more information than necessary, including sensitive or internal data.

We identify misconfigurations in API servers, API gateways, authentication mechanisms, and security controls that could lead to unauthorized access.

We test API resilience against SQL Injection, NoSQL Injection, Command Injection, and other attacks involving malicious input manipulation.

We assess API protection against excessive requests, brute-force attacks, and resource abuse, including proper rate limiting.

We test the security of communication between microservices, including identity and access management and trust between individual components.

Free Report

Discover What Hundreds of Real-World Penetration Tests Reveal

APIs connect web and mobile applications, cloud services, microservices, and internal systems. Download our free Ethical Hacking Report 2025 and discover what we found across 628 penetration tests and an analysis of 3,293 identified vulnerabilities in Citadelo projects.

The most common vulnerabilities found in real-world security projects
How vulnerabilities have evolved compared to 2024
Analysis of APIs, web applications, cloud environments, infrastructure, and AI
Practical recommendations from experienced ethical hackers

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Choose Your Penetration Testing Type

Penetration Testing

Penetration testing (pentesting) simulates real-world cyberattacks to identify vulnerabilities before attackers can exploit them. Learn how penetration testing works, what types of pentests we perform, what you receive after the test, and how we help you reduce cybersecurity risks.

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Web Applications

We test web applications against attacks such as SQL Injection, Cross-Site Scripting (XSS), authentication flaws, and privilege escalation. Our web application penetration testing follows the OWASP Web Security Testing Guide and OWASP Top 10, with every finding manually verified.

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Mobile Applications

Mobile application penetration testing for Android and iOS assesses the security of sensitive data, APIs, server communication, local storage, and the application's resilience against reverse engineering, rooting, jailbreaking, and other attack techniques.

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AI and LLM Systems

We test the security of AI applications, chatbots, AI agents, and RAG systems. AI penetration testing assesses resilience against prompt injection, jailbreak attacks, sensitive data leakage, model manipulation, and abuse of external tools based on the OWASP Top 10 for LLM Applications.

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Network Infrastructure and Internal Systems

We simulate attacks against internal and external infrastructure, including firewalls, VPNs, Active Directory, servers, and databases. Network penetration testing assesses network configuration, segmentation, privilege escalation, and an attacker's ability to move laterally across the environment.

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Cloud Environments

We assess the security of AWS, Microsoft Azure, and Google Cloud Platform (GCP) environments by simulating real-world attacks. Cloud penetration testing covers IAM, cloud storage, Kubernetes, network rules, and exposed services.

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