owasp-security

owasp-security is a skill for Claude Code, Codex from JotJunior/cstk. It costs 109 tokens per session (6,811 once invoked), scanned A, original, MIT.

A checklist for reviewing code and designs against common security standards, including OWASP guidance, authentication rules, API risks, and AI-related threats.

In plain words
What is it for?
Use it for security reviews, vulnerability checks, threat models, authentication code, and MCP security checks. OWASP is a widely used collection of web-application security guidance.
Why use it?
It helps find likely security problems in a code change or project before they are missed. It is a starting review, not a formal security audit or penetration test.

Skill for Claude CodeCodex

Part of the cstk plugin — 21 skills, 7 commands, 7 agents, 1 MCP server shipped together

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/jotjunior/cstk/owasp-security
Any agent
npx skills add JotJunior/cstk --skill owasp-security
Clone the repo
git clone --depth 1 https://github.com/JotJunior/cstk

Made for: Claude Code, Codex.

Or install cstk, the plugin that ships this one along with the rest of its 21 skills, 7 commands, 7 agents, 1 MCP server.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for owasp-security

README.md
[![agentmods](https://agentmods.dev/badge/skills/jotjunior/cstk/owasp-security.svg)](https://agentmods.dev/skills/jotjunior/cstk/owasp-security)
Your own site
<a href="https://agentmods.dev/skills/jotjunior/cstk/owasp-security"><img src="https://agentmods.dev/badge/skills/jotjunior/cstk/owasp-security.svg" alt="Measured on agentmods" height="20"></a>
Per session 109 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 6,811 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 2 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 $0.00109 $0.06811
Opus 5 $0.00055 $0.03406
Sonnet 5 $0.00022 $0.01362
Haiku 4.5 $0.00011 $0.00681

Measured 5d ago against content hash 3eddd13f2180, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

owasp-security scanned grade A with 2 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 5d 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

6. **Standard Library:** Historic CVEs in std libs (Python urllib, Java XML, Ruby OpenSSL).

Runs shell commandslowCapability

Expected in a hook, worth knowing in a rule or an instructions file.

os.system(f"convert {filename} output.png")
plugins/cstk/skills/owasp-security/SKILL.md · 678 lines

How it starts

The opening of the file, as written. The whole thing — 678 lines — stays where its author put it; the contents beside it link to each section on GitHub.

OWASP Security Best Practices Skill

Apply these security standards when writing or reviewing code.

Scope & limits. This skill is a checklist-guided review assistant over the standards below — useful for sweeping a diff or PR and surfacing high-signal findings. It is not, and does not replace, a formal audit, pentest, or certification: the breadth of the catalog (10+ frameworks) means checklist coverage, not exhaustive verification. Use it to raise the security floor and to prioritize; treat findings as starting points, not verdicts.

Deep references

This file is the operational entry point — quick checklists and code patterns. For deep coverage of any topic below, open the matching file in references/:

Topic File
LLM Top 10:2025 + Agentic 2026 deep dive + MCP security + modern prompt injection + MAESTRO references/llm-agentic.md
OWASP API Security Top 10:2023 + OWASP CI/CD Top 10 (PPE, OIDC federation, signing) references/api-cicd.md
NIST SP 800-63B-4 + WebAuthn/Passkeys + OAuth 2.1 + FAPI 2.0 references/auth-modern.md
Post-quantum crypto (FIPS 203/204/205) + crypto agility + 2026 secrets management references/crypto-modern.md
CWE Top 25:2025 + Mobile Top 10:2024 + Kubernetes/Docker Top 10 + EU AI Act mapping references/extras.md

The full historical reference document with deeper background on Top 10:2025, ASVS 5.0, and Agentic 2026 is in OWASP-2025-2026-Report.md.

Quick Reference: OWASP Top 10:2025

# Vulnerability Key Prevention
A01 Broken Access Control Deny by default, enforce server-side, verify ownership
A02 Security Misconfiguration Harden configs, disable defaults, minimize features
A03 Supply Chain Failures Lock versions, verify integrity, audit dependencies
A04 Cryptographic Failures TLS 1.2+, AES-256-GCM, Argon2/bcrypt for passwords
A05 Injection Parameterized queries, input validation, safe APIs
A06 Insecure Design Threat model, rate limit, design security controls
A07 Auth Failures MFA, check breached passwords, secure sessions
A08 Integrity Failures Sign packages, SRI for CDN, safe serialization
A09 Logging Failures Log security events, structured format, alerting
A10 Exception Handling Fail-closed, hide internals, log with context

Read the full file on GitHub · 678 lines

Files

What ships with it

7 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. 5d ago First seen · 678 lines · 109 tokens per session scan A 3eddd13f2180

Subscribe to this mod's changes

owasp-security is a skill published in the GitHub repository JotJunior/cstk (23 stars, last pushed yesterday), licensed MIT. It adds 109 tokens to every session and 6,811 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 2 findings (makes network calls, runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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