Professional API Penetration Testing Services for Secure APIs

API penetration testing is a security assessment that simulates real-world attacks against your API endpoints to identify vulnerabilities before malicious actors do. APIs are a primary target for attackers because they directly expose backend logic and data. Testing helps uncover broken authentication, injection flaws, excessive data exposure, and access control issues that automated scanners alone often miss.

Osto's API penetration testing covers all major API types, including REST, GraphQL, SOAP, and gRPC APIs. Whether your APIs are publicly exposed, partner-facing, or internal microservices, our team maps and assesses each endpoint for the full range of OWASP API Top 10 and business-logic vulnerabilities relevant to your specific architecture.

The OWASP API Top 10 is the industry-standard list of the most critical API security risks, including broken object-level authorization, broken authentication, excessive data exposure, and injection flaws. Yes—every Osto API penetration test is structured to systematically test for all OWASP API Top 10 categories, ensuring no critical vulnerability class is overlooked during the assessment.

The duration depends on the number of endpoints, API complexity, and authentication mechanisms in scope. A focused assessment of a single API with 20–50 endpoints typically takes 3–5 business days, including reporting. Larger environments with hundreds of endpoints or complex business logic flows may require 1–2 weeks for a thorough manual and automated assessment.

Automated scanning quickly identifies known vulnerability patterns and misconfigurations across large numbers of endpoints, but it cannot reason about business logic or chain multi-step attacks. Manual penetration testing involves expert testers who think like attackers—exploiting logic flaws, authorization bypasses, and context-specific vulnerabilities that automated tools routinely miss. Osto combines both for maximum coverage.

Osto follows a controlled, non-destructive testing methodology designed to minimize disruption. Testing can be conducted against a staging or pre-production environment to eliminate production risk entirely. If testing in production is required, we coordinate test windows, use rate-limited payloads, and avoid destructive operations to ensure your services remain available throughout the assessment.

Your report includes a full inventory of tested endpoints, every vulnerability found with its CVSS severity rating, the precise endpoint and parameter affected, proof-of-concept evidence demonstrating exploitability, and step-by-step remediation guidance written for developers. An executive summary is also included so stakeholders without a technical background can understand the business risk and overall security posture.

Osto follows strict data handling protocols throughout all engagements. Any sensitive data encountered during testing—such as API keys, tokens, or personal data—is never stored beyond the scope of the engagement and is securely destroyed upon completion. All testing activities are conducted under a formal engagement agreement with clear confidentiality obligations, ensuring your data and business information remain fully protected.