API Penetration Test (VAPT)

Identify and exploit your API vulnerabilities

Why an API penetration test is essential

An Application Programming Interface (API) penetration test actively exploits vulnerabilities in API endpoints — including broken object-level authorisation, broken authentication, and business logic flaws — to determine real-world impact. Unlike an API vulnerability assessment, which identifies weaknesses without exploitation, an API VAPT confirms exploitability and quantifies attacker reach. Swarmnetics conducts API VAPT through Offensive Security Certified Professional (OSCP) and CREST Registered Penetration Tester (CRT) certified consultants, aligned to the Open Web Application Security Project (OWASP) Top 10 API Security Risks – 2023.

When API flaws become unauthorised data access paths

Uncovering hidden API weaknesses before attackers do

In May 2024, a threat actor posing as a Dell partner abused a portal API that lacked object-level authorisation checks and request throttling. Over three weeks, the actor reportedly drove roughly 5,000 requests a minute and extracted 49 million customer records, including names, addresses, and order details. An API VAPT would have exposed both control failures before the abuse began.

Organisations often need to validate API security controls through regular testing, not just scanning. A single compromised endpoint can enable unauthorised access to customer, order, billing, or partner data at scale, generate regulatory liability, and erode trust. An API VAPT surfaces all three before an attacker does.

How API VAPT exposes real attacker paths

Securing APIs to build lasting business trust

Swarmnetics assesses APIs with manual testing techniques aligned to the OWASP Top 10 API Security Risks – 2023. In a black-box engagement, consultants work without documentation or credentials. The aim is to see what an external attacker can discover, reach, and abuse from exposed API endpoints. That is where automated scanners usually stop short in practice. That includes endpoint access issues, information disclosure, manipulation of API inputs, and input validation weaknesses.

Swarmnetics assesses APIs with manual testing techniques aligned to the OWASP Top 10 API Security Risks – 2023. In a black-box engagement, consultants work without documentation or credentials. The aim is to see what an external attacker can discover, reach, and abuse from exposed API endpoints. That requires more than automated scanning. Scanners are useful for signature-based findings and basic endpoint probing. Manual API testing goes further by manipulating requests, testing unauthenticated access paths, and validating input handling, error messages, rate limiting, and information disclosure.

In a grey-box engagement, consultants use API documentation and test credentials to assess the API from both external-attacker and authorised-user perspectives. Our consultants use Burp Suite Professional, Postman, Insomnia, and purpose-built fuzzing tools to confirm exploitability and identify weaknesses that could compromise the security, integrity, or availability of the API and associated data. They examine authentication and authorisation controls across authenticated endpoints. They test whether requests are properly sanitised and validated, and review how the API handles error messages, rate limiting, and whether users can access objects and functions beyond their intended role. This approach also allows consultants to assess business logic flaws and transaction abuse that only become visible when valid user workflows and multiple privilege levels are exercised.

Yes, we are CREST accredited

Our core team is based in Singapore and consists of CREST certified penetration testers who are also Offensive Security Certified Professional (OSCP) certified. The team has delivered numerous penetration testing projects for customers in Singapore and other locations, from large multinational enterprises to small and medium business, and across various industries.

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Inside the API attack surface

What gets tested

An API VAPT covers the following scope, drawn from the OWASP Top 10 API Security Risks – 2023:

Broken object-level authorisation by manipulating object identifiers
Insecure direct object references across REST and GraphQL endpoints
Authentication flaws in JWT validation, OAuth flows, and brute-force protections
Broken function-level authorisation on privileged endpoints
Mass assignment vulnerability through unauthorised property injection
Unrestricted access to sensitive business flows and transaction abuse
Security misconfiguration in debug endpoints, HTTP methods, and error leakage
Excessive data exposure, rate-limiting gaps, SSRF, and injection flaws

FAQ

An API vulnerability assessment identifies weaknesses in endpoints but stops short of proving attacker impact. An API VAPT goes further: it exploits the weaknesses, chains them where relevant, and shows the practical impact. That distinction matters because business logic flaws and broken object-level authorisation often look low-risk until someone demonstrates how they can be abused.

An API VAPT tests against the OWASP API Security Top 10 – 2023, with attention to broken object-level authorisation, mass assignment, and business logic abuse. It also covers injection flaws, security misconfiguration, excessive data exposure, rate-limiting weaknesses, and server-side request forgery across REST and GraphQL endpoints.

For most API environments, grey-box is the better option. With API documentation and test credentials, our consultants can assess both unauthenticated and authenticated paths, including authorisation logic between roles that black-box testing often cannot reach. Black-box remains useful when the goal is to simulate a purely external attacker.

A compromised API endpoint can expose far more than one record. A broken object-level authorisation flaw may let an attacker read or modify other users’ data simply by changing an identifier in a request. The impact can extend to account takeover, privilege escalation, mass data extraction, and business-process abuse.

An API penetration test from Swarmnetics produces a draft report for your review, followed by a final report upon acceptance. The report includes an executive summary, a detailed technical section with every finding listed by CVSS severity, proof-of-concept evidence demonstrating exploitability, and specific remediation guidance. After you have addressed the findings, we conduct a follow-up retest to confirm adequate remediation.

Any organisation that operates APIs that handle customer or sensitive data should consider an API penetration test. It is particularly relevant for organisations subject to regulatory, contractual, or industry security requirements, which requires regular penetration testing of API endpoints. An API penetration test is also recommended before launching new API endpoints, after significant changes, and as part of an ongoing security assurance programme. Swarmnetics has conducted API penetration tests across all sectors since 2015.

The duration of an API penetration test depends on the scope — the number of API endpoints, their complexity, and whether a black-box or grey-box approach is used. A typical API security assessment takes three to ten business days for the assessment phase, followed by an initial report within five business days for your review.

An API penetration test is often required for compliance with applicable regulatory, contractual, or industry security obligations where organisations must demonstrate that API security controls are effective through regular testing, not just scanning. Swarmnetics recommends conducting an API penetration test at least annually, after significant changes, and before launching new API systems into production.

Every API penetration test follows a three-phase process. In the planning phase, Swarmnetics agrees the scope, testing approach, and schedule with your team. In the Assessment phase, our OSCP and CREST-certified consultants conduct manual API security testing using the OWASP API Security Top 10 methodology to identify and actively exploit vulnerabilities, determining their real-world impact. In the reporting phase, we deliver a draft report for review and a final report with detailed remediation guidance for every finding.

All Swarmnetics penetration tests are conducted by our Singapore-based team of security consultants holding the Offensive Security Certified Professional (OSCP) and CREST Registered Penetration Tester (CRT) credentials. Swarmnetics has been delivering technical security assessments to organisations across Singapore since 2015 and acts as a trusted VAPT delivery partner to service and solution providers, supporting their customers across multiple sectors.

The security assessment report includes specific, actionable remediation guidance for every finding — not generic advice. For each vulnerability, we describe the fix, its priority based on CVSS severity, and any dependencies between remediation steps. Once your team has addressed the findings, Swarmnetics conducts a follow-up retest to verify that each vulnerability has been adequately remediated. The final report confirms closure and provides documented evidence of remediation.