Glossary / API Security Testing
API Security Testing
API security testing evaluates REST, GraphQL, gRPC, and other APIs to confirm authentication, authorization, input validation, and rate limits work as intended where data and actions are exposed.
APIs are the primary interface between clients, services, and sensitive data. Testing focuses on how identities are verified, how resource ownership is enforced, and how inputs are handled across common API patterns.
A typical assessment enumerates endpoints (including undocumented ones) and verifies object-level authorization, property-level controls, rate limiting, and error handling. Business-critical workflows such as checkout, transfers, or admin actions are tested for logic bypasses using safe, non-destructive methods.
The outcome is a clear record of what was in scope, which endpoints were exercised, and any findings with reproduction steps and remediation guidance for review and prioritization.
Common API security vulnerabilities
Most API issues come from how identities, object ownership, and limits are enforced across endpoints. We map these patterns because they explain how attackers move through real workflows and where controls need verification during testing.
Broken object level authorization (BOLA)
Requests can access or update records that belong to other users or tenants because ownership checks are missing or inconsistent.
Resolution: We test read and write paths with controlled identifiers to confirm object ownership is enforced across every endpoint.
Broken function level authorization
Endpoints intended for admin, partner, or support roles are reachable by standard users due to weak role checks.
Resolution: We validate role and scope checks across the full endpoint matrix and confirm explicit denial for out-of-role access.
Excessive data exposure and mass assignment
Responses include fields that should be hidden, or update endpoints accept fields that should not be client-controlled.
Resolution: We review field allowlists and attempt over-posting to ensure only approved fields are readable or writable.
Missing rate limits and abuse controls
Authentication, search, or enumeration endpoints allow high-volume requests that enable brute force and scraping.
Resolution: We run controlled bursts to confirm per-user and per-IP limits, along with appropriate throttling and monitoring.
Input handling and workflow bypass
Query filters, sorting, or workflow steps accept unexpected inputs that change business logic or skip required steps.
Resolution: We exercise edge-case inputs and multi-step flows to verify validation and state transitions hold under misuse.
OWASP API Security Top 10 (2023) mapped to real test cases
The OWASP API Top 10 is a baseline taxonomy. In Appsecco testing, we translate each category into concrete, scoped test cases so your assessment shows how these risks apply to your endpoints, data model, and business workflows.
Broken Object Level Authorization (BOLA/IDOR)
Object ownership checks are inconsistent, allowing access to resources outside the caller's scope.
Resolution: We validate ownership controls across read and write endpoints with controlled identifiers.
Broken Authentication
Authentication flows are inconsistent or incomplete, creating paths to bypass identity checks.
Resolution: We review token lifecycles, login protections, and error handling for bypassable paths.
Broken Object Property Level Authorization
Responses include restricted fields or updates accept properties that should be server-controlled.
Resolution: We test field allowlists so only approved properties are readable or writable.
Unrestricted Resource Consumption
Limits on requests, pagination, or exports are missing or inconsistent across endpoints.
Resolution: We exercise rate limiting and pagination controls on sensitive or high-volume paths.
Broken Function Level Authorization
Role or scope checks for privileged actions are missing or only partially enforced.
Resolution: We confirm role and scope boundaries across admin, partner, and support endpoints.
Unrestricted Access to Sensitive Business Flows
High-value workflows can be automated without safeguards or step verification.
Resolution: We test workflows like checkout, transfers, and invites for guardrails and step validation.
Server-Side Request Forgery (SSRF)
URL-fetching endpoints can be used to access internal services or metadata.
Resolution: We validate URL handling, allowlists, and egress controls for fetchers and webhooks.
Security Misconfiguration
CORS, headers, error handling, and infrastructure settings expose unnecessary risk.
Resolution: We verify production-safe defaults, least-privilege configuration, and minimal disclosure.
Improper Inventory Management
Deprecated or undocumented endpoints remain reachable and bypass newer controls.
Resolution: We inventory shadow APIs, legacy versions, and undocumented routes in scope.
Unsafe Consumption of APIs
External API responses are trusted without validation, affecting downstream decisions.
Resolution: We test how external responses are validated, constrained, and safely handled.
API security testing methodology
We begin with a fixed, written scope that lists the endpoints, environments, and test data in use. This keeps the engagement predictable and makes it clear what will be exercised and what will not.
Testing is manual and workflow-focused. We validate authentication, authorization, and business logic using safe, non-destructive requests that avoid altering customer data or creating operational risk.
Each step maps to documented test cases with evidence. Findings include clear reproduction steps and prioritized fix guidance so reviews are straightforward for engineering and security.
The engagement runs on a defined timeline with a final report and walkthrough. There are no surprise add-ons or scope changes unless you request them.
Tools vs. manual testing for APIs
Automated scanners are a sensible baseline for API testing. They help enumerate endpoints, catch well-known patterns, and provide quick signal without asking you to rework your process.
APIs are defined by identity, ownership, and business workflows. Those controls are specific to your data model and can look correct in isolation, which is why manual judgment is still required to validate real authorization paths.
Manual testing focuses on how requests chain together across flows like onboarding, checkout, and administrative actions. We use safe, controlled requests so results are meaningful without creating operational risk.
In practice, Appsecco combines tool-assisted coverage with manual, workflow-driven review and documents where each method was used. The goal is a defensible assessment that explains what was verified and why.
Related glossary terms
Where human-led testing validates workflow abuse that scanners miss.
How scoped, evidence-based testing confirms real attack paths.
Identity boundaries and access control risks that APIs depend on.
Testing cloud configurations and exposed storage that APIs rely on.
Safe next step
Talk through your API testing scope.
No commitment required.
If you are planning an assessment, we can map the endpoints, workflows, and environments that matter and explain how we would test them with minimal disruption.
Start a conversationor View a sample report first