API Security Top Ten is a ranked set of the most common and consequential risks that expose application programming interfaces to abuse, data leakage, and unauthorized access. It typically covers authentication, authorization, injection, inventory gaps, misconfiguration, and excessive data exposure, helping teams prioritize controls across API design, deployment, and monitoring.
What the API Security Top Ten covers
The api security Top Ten is a practical risk model for the most important API failure patterns, not just a list of bugs. It concentrates attention on the ways APIs are commonly abused, especially when design, access control, or deployment choices create broad exposure.
What makes the top ten useful is that it groups the issues teams repeatedly miss at scale: broken authorization, weak authentication, excessive data exposure, unsafe object handling, inventory gaps, and misconfiguration. That framing helps practitioners compare API risk across services instead of treating each issue as an isolated defect.
Why API risk concentrates in exposed interfaces
APIs are attractive targets because they often sit directly on business logic and data access paths. A small weakness in one interface can expose records, actions, or functions that would otherwise be protected by a user interface or a different trust boundary.
API abuse is especially dangerous when the interface is designed for legitimate automation but lacks equivalent scrutiny for machine-to-machine traffic. Weak request validation, permissive scopes, and inconsistent object checks can let attackers move from a single request to broad enumeration, tampering, or extraction.
Common failure patterns in API security
The most consequential API failures usually fall into a few recurring patterns. Broken object-level authorization, broken function-level authorization, and insecure authentication are especially damaging because they turn normal requests into unauthorized access.
Other frequent problems include excessive data exposure, mass assignment, unrestricted resource consumption, SSRF, and poor inventory management. Each one changes the blast radius differently, but all of them make it easier for an attacker or untrusted client to reach data or functions that were never meant to be public.
How organisations use the top ten in practice
Teams use the top ten as a prioritisation tool for API design reviews, testing, runtime monitoring, and remediation planning. It gives security and engineering a shared language for deciding which controls matter most before deployment and which weaknesses need immediate attention after release.
It is most effective when paired with an API inventory, secure authentication and authorization design, schema validation, rate limiting, and logging that can show who called what, when, and from where. For a deeper control-oriented reference, see API Security Guide, which maps the top risks to preventive controls and testing practices.
Risk and Threat Considerations
APIs often expose the most direct path to sensitive data and high-value functions, so weaknesses can produce immediate confidentiality and integrity loss. If inventory is incomplete, an API is left overly permissive, or object checks are missing, attackers can harvest data at scale or invoke functions outside their intended scope.
Failure mechanism: Attackers exploit weak authorization, hidden or forgotten endpoints, and overly broad access paths to reach records or actions that appear protected but are not consistently enforced at the API layer.
Impact: The result can be account-level abuse, bulk data exposure, unauthorized transactions, service disruption, or a long-running compromise that remains invisible until after significant data has already been accessed.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP API Security Top 10 provides the primary governance reference for this term.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP API Security Top 10 | API1 — Broken Object Level Authorization | API object access control is central to this term. |
| API2 — Broken Authentication | API security top risks include weak or missing authentication. | |
| API5 — Broken Function Level Authorization | Function privilege separation is a core API security risk. | |
| Recommendation — Enforce object-level authorization checks on every API request. Harden API authentication and reject unauthenticated or weakly authenticated calls. Verify caller privilege before every sensitive API action. | ||
Practitioner Guidance
Why practitioners should care: The top ten is most useful when it drives concrete engineering decisions, not when it is treated as a compliance checklist. It should influence how APIs are designed, reviewed, tested, and monitored across their full lifecycle.
What to watch for: Pay close attention to APIs that were added quickly, evolved without a clear inventory, or expose sensitive business functions through generic object identifiers and broad scopes. These are the places where authorization gaps and data overexposure are most likely to persist.
Practitioner takeaway: A strong API security programme starts with knowing every API you expose, then proving that each one authenticates, authorizes, validates, and logs requests in a way that matches the data and actions it controls.
Related resources from NHI Mgmt Group
- How should security teams use the OWASP NHI Top 10 to prioritise risk reduction across service accounts, API keys, and OAuth apps?
- How should security teams prioritize fixes for the most common OWASP API Top 10 failures first?
- How should security teams integrate OWASP API Top 10 risks into the development lifecycle?
- What is the difference between OWASP Top 10 coverage and OWASP API Top 10 coverage for application security teams?