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API Authorization

Security, Risk & Compliance

Pronunciation: A-P-I aw-thur-uh-ZAY-shun

Definition

API authorization determines which endpoints, objects, fields, and actions an authenticated identity may access under defined policies and context. API authorization enforces what a verified user, application, or service is permitted to do.

Overview

Contents Hide
  1. Meaning in plain language
  2. How it works
  3. Where people get it wrong
  4. Related concepts
  5. Reference

Meaning in plain language

API authorization determines which endpoints, objects, fields, and actions an authenticated identity may access under defined policies and context. API authorization enforces what a verified user, application, or service is permitted to do.

How it works

API authorization enforces what a verified user, application, or service is permitted to do. Checks may operate at endpoint, function, object, property, tenant, transaction, or workflow level and can incorporate roles, attributes, ownership, scopes, and risk conditions.

Common failures occur when an API trusts identifiers supplied by the client, checks only broad roles, exposes hidden fields, or applies different rules across similar endpoints. Authentication alone does not prevent one valid user from accessing another user's data.

Authorization should be centralized where practical, deny by default, and execute server-side for every request. Tests must cover horizontal and vertical privilege escalation, while logs should record sensitive grants, denials, policy changes, and exceptional administrative access.

For API Authorization, teams should measure unnecessary friction, exclusion, delay, privacy intrusion, failed recovery, and inconsistent treatment while preserving the safeguards needed for material application and service exposure.

For API Authorization, the trust decision should establish API authorization determines which endpoints, objects, fields, and actions an authenticated identity may access under defined policies and context.

Where people get it wrong

An object ID is not an access token. Enforce ownership or role rules on every read, update and payout function; distinguish object-level from function-level authorization.

API Security, API Credential Separation, Webhook Verification.

Reference

OWASP API Security Top 10 (2023).

Example

Two merchants both have valid API keys. Merchant A requests invoice 123 belonging to Merchant B. Authentication establishes who is calling, but authorization must reject access to B’s record even if the ID is guessed correctly.

Comparison

Authentication verifies the calling identity; authorization checks whether that identity may access this exact object or function.

Key Takeaway

API authorization must protect each object and action, because a valid login does not justify access to every available resource.

Sources

  1. IETF RFC 9110 — IETF (2026-07-30)
  2. OpenAPI Initiative Documentation: V3.2.0 — OpenAPI Initiative (2026-07-30)