Run This Week: API Security Checklist Aligned to OWASP & NIST for Devs

This checklist maps the OWASP API Security Top 10 and NIST lifecycle controls into a prioritized, testable set of design and runtime checks. Start by producing an authoritative API inventory and running an authenticated BOLA test against your highest-value endpoints. Success looks like this: no unauthorized object access on key endpoints and automated tests wired into your CI pipeline.

TL;DR:

• Prioritize establishing a comprehensive API inventory and run authenticated BOLA tests on key endpoints before deployment to prevent unauthorized object access.
• Enforce server-side authorization checks on all resource IDs, restrict long-lived tokens, and validate token attributes on every request to block common access flaws.
• Implement schema validation, size limits, and response shaping to prevent data exposure, mass assignment, and malicious payloads at both design and runtime stages.
• Apply token- and user-based rate limits, return appropriate status codes like 429, and test for resource exhaustion to mitigate outages and abuse.
• Maintain strict control over shadow endpoints, enforce API versioning policies, and embed security checks into development sprints to minimize hidden risks.

Table of Contents

• What this checklist covers and how to use it
• Design-time controls and API lifecycle hygiene
• Authentication and authorization: stopping BOLA, BFLA, and BOPLA
• Input validation, schema enforcement, and data protection
• Traffic control: rate limiting and resource protection
• API inventory, versioning, and eliminating shadow endpoints
• Runtime monitoring, logging, and alerting for API-specific threats
• Security testing in CI/CD and a penetration testing checklist
• Transport security, headers, CORS, and safe error handling
• Secrets, key management, and credential hygiene
• A prioritized checklist you can run this week
• How WVE Labs applies this checklist on client engagements
• Get help building APIs that pass this checklist
• Sources
• FAQ

What this checklist covers and how to use it

The checklist spans ten categories: design, authorization, input handling, transport, traffic control, inventory, monitoring, testing, secrets, and error handling. Each maps to specific entries in the OWASP API Security Top 10 and to the pre-runtime and runtime stages defined in NIST SP 800-228.

• Design and inventory controls belong in pre-runtime, before code ships.
• Authorization, traffic, and monitoring controls operate continuously at runtime.
• Testing and secrets management span both stages and should gate releases.

Prioritize by business impact first, then add each check as a CI gate so regressions fail builds rather than reach production.

Design-time controls and API lifecycle hygiene

Most API breaches trace back to decisions made before a single request hits production. NIST SP 800-228 frames this as a lifecycle problem: controls chosen during design determine what runtime enforcement can actually catch.

1. Maintain an authoritative API inventory and require an OpenAPI contract for every new endpoint before it merges.
2. Threat-model sensitive business flows (payments, account recovery, data export) and document the exact authorization rules each flow requires.
3. Avoid predictable sequential IDs in resource paths; design every data access path around explicit, server-side ownership checks.
4. Publish a formal versioning and deprecation policy, and pair it with automated discovery so undocumented endpoints get flagged, not forgotten.

Skipping this stage does not save time. It moves the cost downstream, where fixing a design flaw means patching production code under pressure instead of catching it in a pull request.

Authentication and authorization: stopping BOLA, BFLA, and BOPLA

Broken Object Level Authorization and Broken Function Level Authorization sit at the top of the OWASP API Security Top 10, and both stem from the same root cause: a token proves identity, not permission. Every endpoint that accepts a resource ID needs its own ownership check, evaluated server-side, on every request.

• Use OAuth 2.0 Authorization Code with PKCE, or OpenID Connect, for user-facing flows, per the OWASP OAuth2 Cheat Sheet.
• For high-value operations, add sender-constrained tokens through DPoP or mTLS so a stolen token alone is not enough.
• Validate token audience, scope, issuer, and expiration on every call, not just at login.
• Keep access token lifetimes short and rotate refresh tokens; require MFA on admin and management endpoints.
• Enforce authorization at both the gateway and the service level. Gateway checks catch obvious abuse early; service-level checks stop bypass attempts and support cached policy decisions without sacrificing correctness.

Pro Tip: Write one automated test per endpoint that attempts cross-user access with a valid token belonging to a different account, then run it in CI on every pull request.

Input validation, schema enforcement, and data protection

Excessive Data Exposure and mass assignment both come from APIs that trust the client to send only what it should. Schema enforcement flips that assumption. Every request and response gets validated against a contract, and anything unexpected gets rejected rather than silently processed.

• Enforce OpenAPI or JSON Schema validation on every endpoint and reject requests with unexpected fields.
• Set explicit size limits on payloads to prevent oversized or malformed requests from reaching business logic.
• Use safe, well-maintained parsers for XML and JSON, and canonicalize inputs before processing them.
• Shape API responses to include only fields the caller is authorized to see, checked at the field level, not just the endpoint level.
• Automate tests that specifically probe for mass assignment and excessive data exposure, per the OWASP REST Security Cheat Sheet.

Traffic control: rate limiting and resource protection

An API without rate limits is one slow client away from an outage, and one scripted attacker away from a bill nobody budgeted for. Limits need to key off identity, not just source IP, since a single compromised token can rotate through addresses freely.

• Set per-token and per-user rate limits rather than relying on IP-based throttling alone.
• Return 429 status codes with a Retry-After header so clients can back off gracefully instead of retrying immediately.
• Design exponential backoff and fair-usage policies for shared endpoints.
• Apply stricter quotas to monetized or abusable resources like email and SMS sending endpoints.
• Test for slow-drip attacks and resource exhaustion patterns in staging before they show up in production traffic.

API inventory, versioning, and eliminating shadow endpoints

Shadow APIs, the endpoints nobody remembers deploying, are one of the more common sources of undetected exposure. An accurate inventory is the control that makes every other control possible, because you cannot secure what you cannot see.

• Treat an OpenAPI registry as the single source of truth, and require publishing to that registry as a deployment gate.
• Automate discovery scans that flag any live endpoint missing from the registry.
• Set formal deprecation windows for old versions, using feature flags and tightened access controls rather than an abrupt cutoff.
• Remove or heavily restrict management and debug endpoints before anything reaches production, a specific gap called out in the OWASP REST Security Cheat Sheet.

Runtime monitoring, logging, and alerting for API-specific threats

Logs are only useful if they capture the fields that let you reconstruct what happened. For APIs, that means user ID, token ID, path, parameters, response code, latency, and a request ID on every entry, plus a written audit record for every authorization decision on a high-value operation.

• Log authorization decisions before responding, not after, so a denied request still leaves a trace.
• Alert on cross-tenant access patterns, spikes in authentication failures, and unusual data volume pulled by a single token.
• Feed logs into a SIEM and retain them long enough to support forensic analysis after an incident.
• Treat sudden authorization-failure spikes as a signal worth paging someone, not just logging.

NIST SP 800-228 recommends treating monitoring as a lifecycle stage in its own right, with controls categorized by pre-runtime and runtime phase, which means logging requirements should be defined at design time, not bolted on after launch.

Security testing in CI/CD and a penetration testing checklist

Manual penetration tests catch what automation misses, but they run too infrequently to be the only line of defense. The goal is layered testing: fast automated checks on every commit, deeper manual testing on a schedule.

1. Automate authorization tests, rate-limit tests, and schema validation in CI, and fail the build on any critical regression.
2. Include BOLA and IDOR scenarios directly in your automated test suite, alongside contract validation and fuzzing.
3. Schedule recurring manual penetration tests focused on business logic and multi-step flows that automated tools tend to miss.
4. Document remediation SLAs by severity and track test coverage as a metric your team reviews, not just a box you check once.

Automated tests that simulate authenticated attacks catch business-logic flaws earlier in the pipeline, which reduces how much expensive manual testing time gets spent finding issues a script could have caught first.

Transport security, headers, CORS, and safe error handling

Transport-level mistakes are often the easiest to fix and the most damaging to skip. Enforce HTTPS with TLS 1.2 or higher, per the OWASP REST Security Cheat Sheet, and disable older protocols and weak cipher suites entirely.

• Enable HSTS and disable fallback to insecure connections.
• Apply security headers where relevant and restrict CORS to an explicit origin allowlist, never a wildcard.
• Return sanitized error messages with a request ID for support, and never expose stack traces or internal details.
• Map HTTP status codes precisely: 429 for rate limits, 413 for oversized payloads, 403 and 401 for authorization failures, 405 for disallowed methods.

Secrets, key management, and credential hygiene

Secrets that live in source control eventually leak, whether through a public repository, a shared laptop, or a misconfigured CI log. Managed secret stores remove that risk by keeping credentials out of code entirely.

• Use a managed secret store rather than environment files or hardcoded values, and scan repositories continuously for leaked keys.
• Automate rotation and revocation, and prefer short-lived credentials wherever your architecture supports them.
• For mTLS deployments, plan the full PKI lifecycle: provisioning, revocation, and automated rotation, not just initial issuance.
• Protect refresh tokens with rotation, sender-constraining methods, or both, following the OWASP OAuth2 Cheat Sheet.

Pro Tip: Set a calendar reminder tied to your secret rotation policy. A rotation schedule that only exists in documentation is a rotation schedule that will not happen.

A prioritized checklist you can run this week

Not every item deserves equal urgency. Triage by what an attacker could actually exploit today versus what hardens your posture over time.

1. Critical: build the API inventory, run authenticated BOLA tests on every authorizing endpoint, and confirm HTTPS enforcement everywhere.
2. High: rotate long-lived tokens, apply per-token rate limits, and add schema and authorization tests to CI.
3. Medium: tighten CORS origin allowlists, remove exposed management endpoints, and extend log retention for forensic readiness.

How WVE Labs applies this checklist on client engagements

Security checks work best embedded in the same sprint cadence as feature work, not run as a separate audit weeks before launch. WVE Labs keeps the same senior team across design, engineering, and delivery on every project, which means the person who designs the authorization model is still on the team when it ships. Checkpoints between security review and engineering happen at sprint planning and again before each release candidate.

— Brian

Get help building APIs that pass this checklist

Running through a checklist is one step. Building the API so it passes on the first review is another, and that is where a team that owns both the design and the engineering earns its keep. WVE Labs designs and builds secure APIs as part of full product engagements, from authorization models through CI/CD integration, with the same senior team staying on from strategy through launch.

If you are evaluating outside help for a build like this, our guide on questions to ask an app development company covers what to ask before signing anything. When you are ready to scope a project, start with mobile app development or browse the full services overview to see where secure backend work fits into a larger build.

Sources

For teams building their own reference library, the OWASP API Security Top 10 defines the core risk categories, while NIST SP 800-228 provides the lifecycle framework for pre-runtime and runtime controls. The OWASP REST Security Cheat Sheet and OWASP OAuth2 Cheat Sheet turn those principles into implementation detail. Teams running security awareness programs alongside technical hardening can also reference Cybersecurity Awareness Month resources for training material.

• OWASP API Security Top 10 (2023)
• NIST SP 800-228, Guidelines for API Protection for Cloud-Native Systems
• OWASP OAuth2 Cheat Sheet

FAQ

What is the fastest first step in an API security checklist?

Start with an authoritative API inventory, since you cannot secure endpoints you do not know exist. Follow it immediately with an authenticated BOLA test against your highest-value endpoints, a check the OWASP API Security Top 10 ranks as the leading API risk.

How does BOLA differ from BFLA?

BOLA occurs when a user can access another user’s data object by manipulating an ID, while BFLA occurs when a user reaches a function or endpoint their role should not permit. Both stem from missing server-side authorization checks and both appear in the OWASP API Security Top 10.

Should rate limiting be based on IP address or token?

Token-based or user-based rate limiting is more reliable than IP-based limiting alone, since a single attacker can rotate through many IP addresses using one stolen token. Pairing token limits with clear 429 responses and a Retry-After header gives legitimate clients a way to back off gracefully.

What does NIST SP 800-228 add beyond the OWASP Top 10?

NIST SP 800-228 organizes controls by lifecycle stage, separating pre-runtime design decisions from runtime enforcement, which helps teams decide when in the development process each control belongs. It complements the OWASP API Security Top 10 by giving engineering teams a sequence to follow rather than just a list of risks.

Can WVE Labs help implement an API security checklist for an existing product?

WVE Labs builds and hardens custom APIs as part of full product engagements, with the same senior team handling design, engineering, and delivery throughout. Reach out through the services overview to scope a security-focused engagement.