OWASP API Security Top 10

The field guide to API security.

All ten risks in one place: what each one is, the request that exploits it, and the control that closes it. Built on the current OWASP standard, with a checklist you can run against your own APIs this week.

One reference, not ten open browser tabs.
Real requests and real fixes, not abstractions.
An audit checklist mapped to every risk.

A look inside

One of the ten, in full.

Every risk in the guide is laid out exactly like this.

API1 Broken Object Level Authorization

What it is

The API trusts the ID in the request and forgets to check who is asking. Anyone authenticated can swap that ID and read records that are not theirs.

              GET /api/accounts/12345   -> 200  your account
              GET /api/accounts/12346   -> 200  a stranger's account
            

One digit changed. That is the entire exploit.

Why it slips through

Ownership is never actually checked.
Controls live only in the client.
The team assumes IDs are hard to guess.

How the guide closes it

Check object ownership on every request.
Centralize authorization in one place.
Default to least privilege.

The ten risks

Everything the guide covers.

API1 Broken Object Level Authorization

Users reaching records that belong to someone else by changing an ID.

API2 Broken Authentication

Weak tokens, missing MFA, and sessions that let attackers impersonate users.

API3 Broken Object Property Level Authorization

Exposing or letting users edit fields they were never meant to touch.

API4 Unrestricted Resource Consumption

No limits on requests, uploads, or queries, leading to outages and cloud bills.

API5 Broken Function Level Authorization

Standard users reaching admin-only endpoints and actions.

API6 Unrestricted Access to Sensitive Business Flows

Bots abusing legitimate workflows at scale: scalping, fraud, hoarding.

API7 Server-Side Request Forgery

Tricking your server into calling internal systems and cloud metadata.

API8 Security Misconfiguration

Default credentials, debug modes, and permissive settings shipped to production.

API9 Improper Inventory Management

Shadow and deprecated APIs that nobody is tracking or patching.

API10 Unsafe Consumption of APIs

Trusting third-party APIs without validating what comes back.

#1

Broken Object Level Authorization has held the top spot on the OWASP API Security list since 2019.

Source: OWASP API Security Top 10

Why it matters

These are not edge cases.

Left open, these gaps lead to data breaches, account takeover, financial fraud, and regulatory exposure. The OWASP list exists because the same handful of mistakes keep showing up in real systems. The guide turns each one into something your team can check for and fix.

Why this one

Written to be used, not filed away.

Built on the current standard

Maps directly to the OWASP API Security Top 10, 2023 edition.

Vendor-neutral

Nothing to buy. Works with the stack you already run.

Practitioner-first

Real endpoints and fixes, not abstract theory.

For the whole team

The engineers who ship the endpoints and the leads who answer for them.

Example - replace before launch

"A real quote here - from an engineer, security lead, or CISO who used the guide - is the single highest-impact thing left to add."

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Ten risks, explained once, properly.

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