T-01
API Authentication Security
Evaluate authentication mechanisms, API keys, access tokens, JWT implementations, OAuth flows, token expiration, refresh mechanisms, and potential authentication bypass vulnerabilities.
Services · API Security Testing
API Security Testing & Penetration Testing
Your APIs Connect Everything. Make Sure They Don't Expose Everything.
At Bugquell, we identify critical API vulnerabilities through expert-led, manual penetration testing. From broken authentication and authorization to business logic flaws, we uncover hidden security weaknesses that could expose sensitive data, compromise user accounts, and disrupt business operations.
Overview
What Is API Security Testing?
REST
REST APIs
Endpoints, methods, parameters and request bodies.
GQL
GraphQL APIs
Queries, mutations and field-level authorization.
ODATA
OData Services
And other supported API architectures in scope.
Methodology informed by
OWASP API Security Top 10OWASP Web Security Testing GuideManual-first testing
Tools we use
PostmanBurp Suite Professional
Application Programming Interfaces (APIs) enable communication between applications, services, and systems. They power modern web applications, mobile platforms, SaaS products, financial services, and enterprise integrations.
As organizations increasingly rely on APIs to exchange sensitive information and perform critical business operations, insecure API implementations can create significant security risks.
API Security Testing is a specialized security assessment designed to identify and validate vulnerabilities in API endpoints, authentication mechanisms, authorization controls, data handling, and business workflows.
At Bugquell, our security researchers go beyond automated vulnerability scanning to understand how APIs function, how different users interact with endpoints, and how attackers might exploit weaknesses in API security controls.
Our manual-first approach focuses on identifying vulnerabilities that require deeper investigation, including Broken Object Level Authorization (BOLA), Broken Function Level Authorization (BFLA), privilege escalation, authentication bypass, and complex business logic flaws.
We assess REST, GraphQL, OData, and other supported API architectures based on the agreed scope and application environment.
Coverage
What We Test
T-02
Broken Object Level Authorization (BOLA / IDOR)
Identify vulnerabilities that allow attackers to access, modify, or delete resources belonging to other users or organizations by manipulating object identifiers or API parameters.
T-03
Broken Function Level Authorization (BFLA)
Assess whether users with limited privileges can invoke administrative endpoints, restricted API functions, or operations intended for higher-privileged accounts.
T-04
API Business Logic Vulnerabilities
Investigate API workflows to identify opportunities for bypassing business rules, manipulating transactions, abusing application functionality, or performing unauthorized operations.
T-05
API Input Validation & Injection
Test API parameters, request bodies, headers, and structured inputs for SQL injection, NoSQL injection, command injection, and other applicable injection vulnerabilities.
T-06
JWT & Token Security
Analyze token validation, signature verification, algorithm restrictions, claim handling, token reuse, and potential weaknesses in access and refresh token management.
T-07
GraphQL API Security
Evaluate GraphQL queries, mutations, field-level authorization, introspection exposure, query complexity, batching, and potential unauthorized data access.
T-08
Rate Limiting & Resource Consumption
Assess whether insufficient request restrictions could enable brute-force attacks, resource exhaustion, excessive API consumption, or abuse of sensitive operations.
T-09
API Data Exposure
Identify excessive data exposure, insecure API responses, sensitive information disclosure, and unintended access to confidential records or internal system details.
T-10
Mass Assignment Vulnerabilities
Evaluate whether attackers can manipulate unexpected API request properties to modify restricted fields, account permissions, ownership attributes, or other protected data.
T-11
Multi-Tenant API Security
Test isolation between organizations, tenants, and user accounts to identify cross-tenant data access, unauthorized modifications, and privilege escalation vulnerabilities.
T-12
API Security Misconfiguration
Review relevant API configurations, CORS policies, HTTP methods, error handling, exposed debugging functionality, and insecure endpoint configurations.
Threats
Common API Security Vulnerabilities
01Broken Object Level Authorization (BOLA)
BOLA vulnerabilities occur when APIs fail to verify whether an authenticated user is authorized to access a requested object.
Impact · Unauthorized access to customer records, confidential information, financial data, or resources belonging to other users.
02Broken Function Level Authorization (BFLA)
BFLA vulnerabilities arise when APIs fail to enforce appropriate permissions for sensitive functions.
Impact · Privilege escalation, unauthorized administrative actions, and modification of restricted application functionality.
03Broken Authentication
Weaknesses in authentication mechanisms may allow attackers to bypass identity verification, misuse access tokens, or compromise user accounts.
Impact · Account takeover, unauthorized API access, and exposure of sensitive information.
04Broken Object Property Level Authorization
APIs may expose sensitive object properties or allow unauthorized modification of restricted fields.
Impact · Sensitive information disclosure, manipulation of protected attributes, and unauthorized permission changes.
05Unrestricted Resource Consumption
Insufficient limits on API requests or resource-intensive operations can allow excessive consumption of application resources.
Impact · Service disruption, increased infrastructure costs, and degraded application availability.
06Broken Business Logic
Security weaknesses in API workflows may allow attackers to bypass intended business restrictions or manipulate application operations.
Impact · Financial loss, unauthorized transactions, workflow manipulation, and abuse of business functionality.
07Server-Side Request Forgery (SSRF)
APIs that process user-controlled URLs or external resource references may allow unauthorized server-side requests.
Impact · Access to internal services, cloud metadata exposure, and interaction with restricted network resources.
08Security Misconfiguration
Improper API configurations, excessive error details, or exposed administrative functionality can increase the attack surface.
Impact · Information disclosure, unauthorized access, and exploitation of improperly secured endpoints.
09Improper API Inventory Management
Outdated, undocumented, or forgotten API endpoints may remain accessible without appropriate security controls.
Impact · Exposure of deprecated functionality, sensitive information, or insecure legacy endpoints.
10Unsafe Consumption of Third-Party APIs
Applications may trust responses from external APIs without sufficient validation or security controls.
Impact · Data manipulation, injection vulnerabilities, and compromise of downstream application functionality.
Methodology
Our API Security Testing Methodology
STEP 1
Scope & API Architecture Review
We begin by understanding the API architecture, business functionality, authentication mechanisms, user roles, and integrations.
Our team establishes the authorized testing scope, supported API environments, and rules of engagement before testing begins.
STEP 2
API Discovery & Endpoint Mapping
Our security researchers use Postman and Burp Suite Professional to explore API functionality, analyze requests and responses, identify endpoints, and understand authentication flows.
We review API documentation, Postman collections, HTTP methods, request parameters, and available functionality to map the API attack surface.
STEP 3
Authentication & Authorization Testing
Using Postman and Burp Suite Professional, we manually manipulate API requests, authentication tokens, headers, parameters, and request bodies to evaluate security controls.
We compare API responses across different users, roles, and tenants to identify BOLA, BFLA, IDOR, privilege escalation, authentication bypass, and unauthorized resource access.
STEP 4
Business Logic & Advanced Security Testing
We use Postman to execute and analyze multi-step API workflows, test different request sequences, and investigate application-specific business rules.
Our researchers examine how API operations interact, identify opportunities to bypass security restrictions, and determine whether multiple vulnerabilities can be chained to demonstrate greater security impact.
STEP 5
Vulnerability Validation & Impact Analysis
Potential vulnerabilities are manually validated through controlled testing using Postman, Burp Suite Professional, and other appropriate security tools.
We evaluate exploitability, affected resources, required privileges, and realistic business impact while minimizing disruption to the application.
STEP 6
Detailed Security Reporting
We provide a comprehensive API security assessment report documenting validated vulnerabilities, affected endpoints, technical evidence, severity ratings, reproduction steps, and actionable remediation recommendations.
STEP 7
Remediation Support & Retesting
We provide practical remediation guidance to help development teams understand and address identified security weaknesses.
Where included in the engagement, we use Postman and other relevant tools to reproduce previously identified issues and verify whether the implemented security fixes are effective.
Deliverables
What You Receive
D-01
Executive Security Summary
A clear overview of the API security assessment, major findings, business risks, and recommended remediation priorities.
D-02
Detailed Technical Vulnerability Report
Comprehensive documentation of validated vulnerabilities, affected API endpoints, severity classifications, and technical explanations.
D-03
Proof-of-Concept Evidence
Relevant HTTP requests and responses, reproduction steps, screenshots where applicable, and supporting evidence demonstrating the identified weaknesses.
D-04
Risk & Business Impact Assessment
An evaluation of each vulnerability's potential impact on data confidentiality, integrity, availability, and business operations.
D-05
Actionable Remediation Recommendations
Practical security recommendations to help developers address vulnerabilities and strengthen API security controls.
D-06
Retesting & Verification Results
Documentation of remediation verification where retesting is included in the agreed assessment.
Why us
Why Choose Bugquell?
W-01
Manual-First API Penetration Testing
We prioritize hands-on security testing to identify vulnerabilities that automated scanners may overlook, particularly those involving authorization, application workflows, and complex business logic.
W-02
Specialized Authorization Testing
Our security researchers focus on BOLA, BFLA, IDOR, horizontal and vertical privilege escalation, and multi-tenant authorization weaknesses.
W-03
Research-Driven Security Assessments
We investigate how API endpoints, user permissions, and business operations interact to identify security risks beyond isolated endpoint vulnerabilities.
W-04
Real-World Attack Scenarios
We examine how attackers might abuse API functionality or combine multiple security weaknesses to demonstrate realistic security impact.
W-05
Clear & Actionable Reporting
Our reports explain vulnerabilities, supporting evidence, business impact, and remediation recommendations in a format understandable to both technical and non-technical stakeholders.
W-06
ISO/IEC 27001:2022 Certified
Bugquell operates an ISO/IEC 27001:2022-certified information security management system, demonstrating its commitment to structured information security practices.
Ready to scope your APIs?
Request a Security Assessment →FAQ
Frequently Asked Questions
Q01What is API Security Testing?+
API Security Testing is the process of evaluating API endpoints, authentication mechanisms, authorization controls, data handling, and business workflows to identify vulnerabilities that could expose sensitive information or enable unauthorized operations.
Q02What types of APIs does Bugquell test?+
Bugquell assesses REST APIs, GraphQL APIs, OData-based services, and other supported API architectures, depending on the agreed testing scope and application environment.
Q03What is the difference between API Security Testing and Web Application Penetration Testing?+
Web Application Penetration Testing evaluates the security of web application functionality, including browser-based interactions and server-side behavior.
API Security Testing focuses specifically on API endpoints, request and response handling, authentication, authorization, data exposure, and API-specific business logic.
Q04Can API vulnerabilities exist even when authentication is implemented correctly?+
Yes. An API may correctly authenticate users but fail to verify whether they are authorized to access specific resources or perform particular operations.
Such weaknesses can result in BOLA, BFLA, IDOR, and privilege escalation vulnerabilities.
Q05Do you test APIs with multiple user roles and tenants?+
Yes. We assess authorization boundaries between users, roles, and organizations to identify unauthorized access, cross-tenant data exposure, and privilege escalation vulnerabilities.
Q06Do you perform manual or automated API security testing?+
Bugquell follows a manual-first testing approach. Tools such as Postman and Burp Suite Professional assist with endpoint discovery, request analysis, and testing efficiency, while our researchers manually investigate application behavior and validate security findings.
Q07How long does an API penetration test take?+
The assessment duration depends on the number of endpoints, API complexity, authentication mechanisms, user roles, integrations, and agreed scope.
We provide an estimated timeline after reviewing the API environment and assessment requirements.
Q08Which security standards do you follow for API testing?+
Our API security testing methodology is informed by the OWASP API Security Top 10, OWASP Web Security Testing Guide, and relevant penetration testing practices.
Attack surface: unknown
Your APIs Are the Backbone of Your Business. Keep Them Secure.
From sensitive customer data to critical business operations, your APIs handle valuable information every day. Partner with Bugquell to uncover hidden vulnerabilities, strengthen authorization controls, and reduce exposure to real-world API security threats.