api-security

A security review of REST and GraphQL APIs, which are interfaces that let software exchange data, against the OWASP API Security Top 10.

In plain words
What is it for?
Use it with OpenAPI or Swagger files, API endpoint code, GraphQL schemas, or API gateway settings. It reviews authentication, authorization, input, and endpoint exposure.
Why use it?
It helps find weaknesses such as broken access checks, weak login protection, missing rate limits, and unsafe requests to other services.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/unitoneai/securityskills/api-security
Any agent
npx skills add UnitOneAI/SecuritySkills --skill api-security
Clone the repo
git clone --depth 1 https://github.com/UnitOneAI/SecuritySkills

Made for: Claude Code, Codex.

Per session 74 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,337 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00074 $0.03337
Opus 5 $0.00037 $0.01669
Sonnet 5 $0.00015 $0.00667
Haiku 4.5 $0.00007 $0.00334

Measured 2d ago against content hash 1cc3b44482a0, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

api-security scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/appsec/api-security/SKILL.md · 255 lines

How it starts

The opening of the file, as written. The whole thing — 255 lines — stays where its author put it; the contents beside it link to each section on GitHub.

API Security Review -- OWASP API Security Top 10:2023

A structured, repeatable process for reviewing REST and GraphQL APIs against the OWASP API Security Top 10:2023. This skill produces findings mapped to API1 through API10 with associated CWE identifiers, severity ratings, and actionable remediation guidance. It applies to OpenAPI/Swagger specifications, API endpoint source code, GraphQL schemas, and API gateway configurations.


Step 1: API Inventory and Scope

If a target is provided via arguments, focus the review on: $ARGUMENTS

Before analyzing any endpoint, establish a complete inventory of the API surface under review.

  1. Identify the API style -- REST (OpenAPI/Swagger), GraphQL, gRPC, or hybrid. Each style has distinct attack patterns.
  2. Catalog all endpoints and operations -- For REST, list every path and HTTP method. For GraphQL, list all queries, mutations, and subscriptions.
  3. Map authentication mechanisms -- OAuth 2.0 flows, API keys, JWTs, session cookies, mTLS, or custom tokens. Note which endpoints require authentication and which are public.
  4. Identify authorization models -- RBAC, ABAC, ownership-based, or no authorization. Document how object-level and function-level access control decisions are made.
  5. Catalog data objects -- List the resources/entities exposed by the API and their sensitivity classification (PII, financial, internal, public).
  6. Note rate limiting and quota configurations -- Document any existing throttling, quota, or cost-control mechanisms at the gateway or application layer.
  7. Identify downstream dependencies -- Third-party APIs, internal microservices, or webhooks that the API consumes.

Gate: Do not proceed until the API style, authentication model, authorization model, and endpoint inventory are documented. Incomplete scope leads to missed findings.


Steps 2-11: OWASP API Security Top 10:2023 Evaluation (API1-API10)

Evaluate the API against all ten OWASP API Security Top 10:2023 risk categories: Broken Object Level Authorization (BOLA), Broken Authentication, Broken Object Property Level Authorization, Unrestricted Resource Consumption, Broken Function Level Authorization (BFLA), Unrestricted Access to Sensitive Business Flows, Server Side Request Forgery (SSRF), Security Misconfiguration, Improper Inventory Management, and Unsafe Consumption of APIs.

Read the full file on GitHub · 255 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 255 lines · 74 tokens per session scan A 1cc3b44482a0

Subscribe to this mod's changes

api-security is a skill published in the GitHub repository UnitOneAI/SecuritySkills (58 stars, last pushed 2mo ago), licensed MIT. It adds 74 tokens to every session and 3,337 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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