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APIs are your application’s most exposed attack surface. They’re the primary target for attackers, and they’re where the most impactful vulnerabilities live: broken access control, authentication bypasses, data exposure, and business logic flaws that let attackers manipulate your application in ways your team never anticipated. Most API security testing is limited to schema validation or basic fuzzing. These approaches catch formatting issues and simple injection patterns, but they miss the vulnerabilities that matter most: authorization flaws that let one user access another’s data, multi-step flows that can be manipulated out of sequence, rate limiting gaps that enable brute force attacks, and business logic issues that only emerge when an attacker understands how your API actually works.

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How Neo Solves This

Neo tests your APIs the way an attacker would approach them: by understanding the application logic, mapping relationships between endpoints, and testing for vulnerabilities that require context and multi-step interaction.
  1. Discovers and maps your API — Neo crawls your API, ingests OpenAPI/Swagger specifications if available, and builds a complete map of endpoints, parameters, authentication mechanisms, and relationships between resources.
  2. Tests authentication and authorization deeply — Neo tests every endpoint with different privilege levels: unauthenticated, regular user, and admin. It checks whether horizontal access control is enforced (can user A access user B’s resources?), whether vertical escalation is possible (can a regular user reach admin endpoints?), and whether authentication can be bypassed entirely.
  3. Explores business logic — Neo understands multi-step API flows (checkout sequences, state machines, approval workflows) and tests whether steps can be skipped, reordered, or manipulated. It tests for race conditions, price manipulation, quantity tampering, and other logic flaws that schema validation cannot detect.
  4. Fuzzes with context — rather than blindly fuzzing every parameter, Neo uses its understanding of the API’s structure to craft targeted payloads. It identifies which parameters flow into database queries, which are reflected in responses, and which control application behavior, then tests accordingly.
  5. Chains findings into attack paths — an information disclosure on one endpoint might reveal internal IDs that enable an IDOR on another endpoint, which exposes data that allows account takeover through a third. Neo pursues these chains to demonstrate real impact.

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What This Looks Like in Practice

You ask Neo to assess your API: 
Test our REST API at https://api.staging.yourapp.com

OpenAPI spec: https://api.staging.yourapp.com/docs/openapi.json

Credentials:
- Admin: Bearer eyJhbG... (admin token)
- User: Bearer eyJhbG... (regular user token)

Focus on broken access control, injection, authentication 
bypass, and any business logic issues in the payment and 
user management endpoints.
Neo ingests the spec, identifies 83 endpoints across 12 resource groups, and begins testing. It discovers that the /api/v1/users/{id}/billing endpoint returns billing details for any user ID when called with a regular user token — a horizontal privilege escalation that exposes payment information for all customers. The finding includes the exact request, the response showing another user’s data, and guidance on implementing proper ownership validation.

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What You Get

  • Full API coverage — every endpoint tested across authentication levels and privilege boundaries
  • Authorization testing at depth — horizontal and vertical access control validation that goes beyond simple role checks
  • Business logic testing — multi-step flow manipulation, race conditions, and application-specific logic flaws
  • Contextual fuzzing — targeted injection testing based on how your API actually processes input
  • Chained attack paths — findings connected into realistic attack scenarios that demonstrate business impact
  • Evidence for every finding — exact requests, responses, and reproduction steps

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Setup

To run API security testing:
  1. Add your API environment in Settings → Environments
  2. Configure authentication tokens or API keys in Settings → Environment Variables
  3. Optionally provide an OpenAPI/Swagger specification URL for faster discovery
  4. Start a new conversation and tell Neo what to test