API Security Field Manual & OWASP API Top 10 Red Teaming Checklist (2026 Edition)
Modern mobile applications, single-page web apps, and microservice architectures communicate entirely through APIs. This offensive and defensive field manual guides security testers and developers through auditing the OWASP API Security Top 10 (2026 update), covering Broken Object Level Authorization (BOLA), Broken Function Level Authorization (BFLA), Mass Assignment, and shadow API endpoint discovery.
Interactive Technical Checklist (12 Verification Checkpoints)
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[Authorization & Access] Test for BOLA by changing resource IDs in API requests (/api/users/{id}/statement) between distinct authenticated sessions.Mandate: OWASP API1 / NPCI Mandate
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[Authorization & Access] Test for BFLA by invoking administrative endpoints (/api/admin/users) using regular user authorization tokens.Mandate: OWASP API5
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[Authentication & Tokens] Verify JWT signature validation; test for algorithm confusion attacks (RS256 to HS256) and expired token acceptance.Mandate: OWASP API2
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[Authentication & Tokens] Enforce strict token revocation upon user password reset or session logout across all microservices.Mandate: Session Hygiene
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[Input Validation & Mass Assignment] Verify that DTO schemas reject unexpected JSON payload properties (e.g., isAdmin=true, role=admin).Mandate: OWASP API3
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[Input Validation & Mass Assignment] Test SSRF vectors in endpoints accepting webhooks, avatar URLs, or callback links; block internal IP ranges.Mandate: OWASP API7
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[Rate Limiting & DoS Defense] Test API endpoints for rate limiting; verify rejection of brute force attempts on OTP, password reset, and login endpoints.Mandate: OWASP API4
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[Rate Limiting & DoS Defense] Enforce maximum payload size limits and query execution timeouts across all API gateway routes.Mandate: Resource Consumption
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[API Inventory & Governance] Decommission or restrict access to legacy v1/v2 API endpoints (Zombie APIs) that lack current security controls.Mandate: OWASP API9
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[API Inventory & Governance] Ensure production API responses do not leak sensitive stack traces, SQL syntax, or internal server IPs in error messages.Mandate: OWASP API8
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[GraphQL Hardening] Disable GraphQL introspection in production; configure query depth limit (≤ 5 levels) to prevent DoS.Mandate: GraphQL Defense
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[Logging & Telemetry] Log all failed API authentication attempts and BOLA authorization failures to SIEM while masking sensitive PII.Mandate: CERT-In 180-Day Rule
APIs expose the underlying business logic of applications directly to clients. Traditional web application firewalls (WAFs) looking for simple SQL injection strings fail to detect logical authorization flaws like BOLA, where an attacker requests another user's private data using valid credentials.
Vulnerability Breakdown: BOLA vs BFLA
Occurs when an API endpoint uses client-supplied input to access an object without checking if the requester has permission to that specific object.
Authorization: Bearer [User_A_Token]
Response: Returns User_B invoice details!
Occurs when an API endpoint relies on hiding administrative endpoints or obfuscated URL paths without verifying the user's role on the server.
Authorization: Bearer [Regular_Customer_Token]
Response: 200 OK (Exports database dump!)
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