insecure-design

insecure-design is a skill for Claude Code, Codex from scholarly360/owasp-top10-web-skills. It costs 161 tokens per session (2,131 once invoked), scanned A, original, MIT.

A security review guide for finding and fixing insecure designs in Python web apps built with FastAPI or Flask. Insecure design means the system is missing a needed security control by design, rather than merely containing a coding mistake.

In plain words
What is it for?
It is for reviewing architecture, threat models, business rules, file uploads, rate limiting, and tenant isolation, then planning the required design changes.
Why use it?
It helps uncover risks such as weak rate limits, unsafe file-upload designs, race conditions, and missing separation between customers before they become security problems.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit It is for reviewing architecture, threat models, business rules, file uploads, rate limiting, and tenant isolation, then planning the required design changes.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/scholarly360/owasp-top10-web-skills/insecure-design
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.

Any agent
npx skills add scholarly360/owasp-top10-web-skills --skill insecure-design
Clone the repo
git clone --depth 1 https://github.com/scholarly360/owasp-top10-web-skills

Made for: Claude Code, Codex.

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 insecure-design

README.md
[![agentmods](https://agentmods.dev/badge/skills/scholarly360/owasp-top10-web-skills/insecure-design/github.svg)](https://agentmods.dev/skills/scholarly360/owasp-top10-web-skills/insecure-design)
Your own site
<a href="https://agentmods.dev/skills/scholarly360/owasp-top10-web-skills/insecure-design"><img src="https://agentmods.dev/badge/skills/scholarly360/owasp-top10-web-skills/insecure-design/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for insecure-design

Your own site · 80×15
<a href="https://agentmods.dev/skills/scholarly360/owasp-top10-web-skills/insecure-design"><img src="https://agentmods.dev/badge/skills/scholarly360/owasp-top10-web-skills/insecure-design.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 161 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,131 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00161 $0.02131
Opus 5 $0.00081 $0.01066
Sonnet 5 $0.00032 $0.00426
Haiku 4.5 $0.00016 $0.00213

Measured 12d ago against content hash 4b68d91daab4, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

insecure-design 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 12d 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/insecure-design/SKILL.md · 244 lines

How it starts

The opening of the file, as written. The whole thing — 244 lines — stays where its author put it; the contents beside it link to each section on GitHub.

OWASP A06:2025 — Insecure Design

What This Skill Does

Guides detection, analysis, and remediation of Insecure Design vulnerabilities — architecture-level failures where security controls are absent or structurally inadequate. Unlike implementation bugs, insecure design cannot be fixed by patching code alone; it requires redesigning the flow or adding missing control layers.

OWASP 2025 position: #6 (down from #4 in 2021, as threat modeling adoption has improved)
CWEs covered: 39 | Avg incidence: 1.86%
Key CWEs: CWE-434, CWE-269, CWE-362, CWE-799, CWE-602


Core Concepts

Design vs. Implementation

Insecure Design (A06) Implementation Bug (other categories)
Rate limiting never architected into login flow Rate limiter present but misconfigured
File upload stored in web root by design Upload handler missing extension check
No tenant isolation in multi-tenant DB schema Query missing WHERE clause
Business logic allows negative quantities Missing server-side input validation

A design flaw requires adding a new control or refactoring the architecture, not just patching existing code.


Testing Checklist for FastAPI / Flask

1. Rate Limiting (CWE-799)

Verify that login, registration, password reset, and high-value transaction endpoints enforce rate limits.

FastAPI — SlowAPI:

from slowapi import Limiter
from slowapi.util import get_remote_address

limiter = Limiter(key_func=get_remote_address)

@app.post("/login")
@limiter.limit("5/minute")
async def login(request: Request, ...): ...

Flask — Flask-Limiter:

from flask_limiter import Limiter
limiter = Limiter(app, key_func=get_remote_address)

@app.route("/login", methods=["POST"])
@limiter.limit("5 per minute")
def login(): ...

Red flags to flag in review:

  • Login, /register, /reset-password, /checkout routes with no rate-limiting decorator
  • RATELIMIT_ENABLED = False or limiter initialized without being applied to sensitive routes
  • Rate limits too permissive (e.g., 1000/minute on auth endpoints)

Read the full file on GitHub · 244 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. 12d ago First seen · 244 lines · 161 tokens per session scan A 4b68d91daab4

Subscribe to this mod's changes

insecure-design is a skill published in the GitHub repository scholarly360/owasp-top10-web-skills (22 stars, last pushed 5mo ago), licensed MIT. It adds 161 tokens to every session and 2,131 once invoked, about $0.0008 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.

Related

Other skills, from other repositories

Web Application Security Testing

OWASP Top 10 testing, injection vulnerability detection, API security assessment, authentication testing, and web vulnerability reporting for authorized assessments.

Masriyan/Claude-Code-CyberSecurity-Skill · 30 tokens

saferskills

Use SaferSkills to find, evaluate, and safely install AI agent capabilities (skills, MCP servers, hooks, plugins, rules) and to assess a whole agent. Run this before you install, add, recommend, or trust any capability — or when asked whether one is safe or what its score is: scan and score it first with npx…

OpenLatch/saferskills · 91 tokens

content-cadence

Pipeline for turning one R&D artefact (PR, PoC, analysis) into one public post — briefing or deep dive — plus a social derivative where the overlay scopes one in. Triggers when an R&D output is ready to become content, or when drafting any blog post for the site. Enforces the anonymisation gate and repo editorial…

lemur47/logic · 76 tokens

evm

Help users answer one question: "Are we on track?" using Earned Value Management metrics. This skill replaces gut-feel status reporting and traffic-light dashboards with four computed numbers (SV, SPI, CV, CPI) that tell you exactly where a project stands — in schedule and in budget — at any point in time.

lemur47/logic · 0 tokens

tco

Help users answer one question: "What will this actually cost?" using Total Cost of Ownership analysis. This skill replaces sticker-price comparisons with lifetime cost calculations that include maintenance, operations, time value of money, and residual value.

lemur47/logic · 0 tokens

montecarlo

Help users answer one question: "What's the probability we finish by this date?" using Monte Carlo schedule simulation. This skill replaces single-point PERT estimates with full probability distributions over project duration.

lemur47/logic · 0 tokens