Welcome to Perennial Consultancy

API Penetration Testing (VAPT) Service
in Singapore

Your Business Logic can be Bypassed Directly via underlying endpoints

Limited Time Offer (Valid Till September 2026):

Get API VAPT for up to 40 endpoints at just $4,000 SGD.

What is an API Penetration Test?

An API Penetration Test evaluates the security of the backend interfaces that power modern web applications, mobile apps and system integrations. Rather than testing what users see in a browser, it interacts directly with backend APIs to identify vulnerabilities that attackers can exploit.

While a traditional Web Application Penetration test assesses the browser-facing interface, an API Penetration test bypasses the user interface entirely to test the application’s underlying business logic and communication layer.

This helps identify vulnerabilities that may not be exposed through normal user interactions.

Our API VAPT assesses critical backend security controls, guided by the OWASP API Security Top 10, including

  • Multi-tenant data isolation
  • Authentication and access control
  • Business logic vulnerabilities
  • Input validation and data handling
  • Authorization between users and roles
  • Sensitive data exposure
Scope of Assessment

The Strategic Analogy

A traditional web application pentest verifies whether the front door, windows, and physical locks of an office building are secure. An API pentest examines whether someone with legitimate access to the building can enter rooms they shouldn’t, access confidential files, or misuse internal services because access controls are weak.

When is a dedicated API Penetration Test Required?

Securing Third-Party Data Exchanges

B2B Client Portals

Providing custom data feeds or reporting endpoints directly to your paying corporate clients creates highly trusted pipelines. A dedicated API pentest ensures your multi-tenant isolation is flawless, guaranteeing a client cannot manipulate an API request to view a competing company’s private records.

Supply Chain & Vendor

Allowing third-party vendors to connect to your backend APIs to place orders or check stock—such as  logistics providers, supplier webhooks, or payment gateways—opens deep perimeter gaps. Rigorous testing validates that these automated partner links cannot be exploited to bridge into your private corporate network.

Open Application

If your enterprise software allows external developers to build custom integrations or add-ons on top of your platform, you are exposing raw system logic. Regular API Penetest is critical to ensure untrusted third-party code cannot exploit your core authorization structures.

Top 5 Critical API Vulnerabilities

Common OWASP API Top 10 Flaws We Uncovered

OWASP API 1
Broken Object Level Authorization

A malicious user manipulate identifier parameters inside data requests, tricking the application into revealing other users’ data records.

OWASP API 2
Broken User Authentication

Improper verification within authorization signatures, missing login rate limits or poor tracking of issued  authentication tokens. E.g. allowing over 5 concurrent tokens per account.

OWASP API 4
Unrestricted Resource Consumption

Endpoints lacking request rate limits or request size thresholds, allowing attackers to abuse the API beyond its intended use. E.g.  rapidly exfiltrate sensitive data.

OWASP API 6
Unrestricted Access to Sensitive Business Flow

Failure to restrict access to sensitive business flows based on user role. E.g.  Allowing an operator role to update an administrator role’s password. 

OWASP API 8
Security Misconfiguration

Improper configuration of API security controls, such as default settings, unused features, exposure of API documentation set, increasing the attack surface.

Find out if your APIs are Vulnerable

Why Choose Perennial for API Penetration Testing in Singapore

Our Key Differentiators in API VAPT

CSRO Licensed VAPT Provider

Licensed by CSA under CSRO and  onboarded as a CISOaaS VAPT provider, ensuring accountability and regulatory compliance.
Licence No CS/PTS/C-202606-336

CREST Certified

Our consultants hold industry certifications including CREST, CISSP and AWS, backed by over 20 years of practical cybersecurity and infrastructure experience.

Auditor-Ready Attestations with Proof

Standard pentests show what breaks. Positive Attestations show what held — backed by execution logs and evidence, providing strong proof for your auditors.

Our 5-Step API Assessment Methodology
From Scoping to Remediation

Scope

Defines rules of engagement such as scope, schedule, environment, authentication types, and API boundaries

Recon

Gather info on target assets to map out API endpoints critical to business functions and define the attack surface

Assess

Automated and manual testing of authentication, rate limiting, token handling, and input validation etc

Exploit

Align attack vectors with identified vulnerabilities to bypass business logic or extract sensitive data

Report / Retest

Interim and final reports - Executive Summary, POCs, remediation guidance & walkthrough, including retests

FAQ's

We highly recommend a grey box approach for API testing to get the maximum value for your budget:

  • Black Box Testing: Engineers simulate an outsider with zero prior knowledge. They must guess hidden endpoint URLs and parameter names from scratch, which often results in a surface-level assessment.

  • Grey Box Testing: You provide our engineers with API documentation (like Swagger/OpenAPI specs or Postman collections) and test accounts with different privilege levels. This eliminates time-consuming guesswork, allowing our team to immediately jump into deep, context-aware testing.

Not necessarily. Attempting to deeply pentest hundreds of endpoints simultaneously is rarely practical. Instead, we recommend a risk-based, tiered scoping approach to maximize your budget:

  • Tier 1: High Risk (Deep Manual Pentest): Public-facing APIs, authentication gateways, and endpoints handling sensitive data (PII) or financial transactions.

  • Tier 2: Medium Risk (Targeted Assessment): Partner-facing APIs and critical internal microservices. We run focused, time-boxed testing on their primary logic paths.

  • Tier 3: Low Risk (Automated Scanning): Internal, read-only, or non-sensitive APIs covered via automated vulnerability scanning to catch low-hanging fruit.

If your APIs are for your own consumption, not called by external parties like partners and corporate clients, we include them as part of our Web or Mobile VAPT. There is no need to have a separate API penetration test.

Yes, our testing methodology is  guided by the OWASP API Security Top 10 framework. We focus our assessments on the most critical, high-prevalence vulnerabilities and logic flaws within this standard that pose the greatest risk to your business

No. We prioritise operational stability throughout the engagement. During the initial scoping phase, we define clear rules of engagement and agree on the testing approach. Wherever possible, testing should be conducted in a staging or UAT environment that closely mirrors production.

If testing must be performed in production, we use controlled, non-destructive payloads and coordinate closely with your  team to minimise operational risk and avoid service disruption. We also recommend performing a backup before testing begins as a precautionary measure.

To prevent unintended impact, all testing is performed only against the provided test accounts. We do not access or modify other user accounts.

Note: DDoS testing, social engineering and any other disruptive attack techniques are out of scope.

Our report consists of:

  1. Executive Summary
    • Overview of assessment
    • Findings categorized by OWASP API Top 10
    • Attestation on areas you have done well
  2. Risk Register
    • Findings tracker
  3. Engagement scope
    • Scope of work, methodology and risk model used
  4. Detailed Findings
    • Issue details and background
    • Issue remediation
    • Attestation

Our Blog

Latest Articles

Let's Start the Conversation

You can also drop us an email at [email protected]