secure-by-default

secure-by-default is a skill for Claude Code from contactandrewchl-wq/turtle-mcp. It costs 50 tokens per session (556 once invoked), scanned A, original, MIT.

A security checklist for agents that handle user input, produce output, save data, or call external services. It covers validation, escaping, secret handling, and access checks.

In plain words
What is it for?
Use it when writing or reviewing code that handles data, web requests, databases, shell commands, or protected functions.
Why use it?
It helps prevent common problems such as leaking credentials, accepting unsafe input, or allowing unauthorised actions.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the turtle plugin — 26 skills shipped together

Good fit Use it when writing or reviewing code that handles data, web requests, databases, shell commands, or protected functions.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/contactandrewchl-wq/turtle-mcp/secure-by-default
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 contactandrewchl-wq/turtle-mcp --skill secure-by-default
Clone the repo
git clone --depth 1 https://github.com/contactandrewchl-wq/turtle-mcp

Made for: Claude Code.

Or install turtle, the plugin that ships this one along with the rest of its 26 skills.

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 secure-by-default

README.md
[![agentmods](https://agentmods.dev/badge/skills/contactandrewchl-wq/turtle-mcp/secure-by-default/github.svg)](https://agentmods.dev/skills/contactandrewchl-wq/turtle-mcp/secure-by-default)
Your own site
<a href="https://agentmods.dev/skills/contactandrewchl-wq/turtle-mcp/secure-by-default"><img src="https://agentmods.dev/badge/skills/contactandrewchl-wq/turtle-mcp/secure-by-default/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 secure-by-default

Your own site · 80×15
<a href="https://agentmods.dev/skills/contactandrewchl-wq/turtle-mcp/secure-by-default"><img src="https://agentmods.dev/badge/skills/contactandrewchl-wq/turtle-mcp/secure-by-default.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 50 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 556 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 $0.00050 $0.00556
Opus 5 $0.00025 $0.00278
Sonnet 5 $0.00010 $0.00111
Haiku 4.5 $0.00005 $0.00056

Measured 10d ago against content hash d3401a75c728, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

secure-by-default 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 10d 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/secure-by-default/SKILL.md · 49 lines

What it actually says

Secure by default

Cuatro preguntas antes de cada cambio que toque datos, entrada de usuario o un servicio externo.

Lista de control

  1. Entrada — ¿Está validada en el borde (tipo, longitud, formato, rango)? ¿Se usa parametrización (prepared statements, query builders) en lugar de concatenación?
  2. Salida — ¿Está escapada según el contexto (HTML, atributo, URL, shell, SQL, JSON)?
  3. Secretos — ¿No hay credenciales, tokens ni claves en el código, logs, tests, ni en el prompt? ¿Se leen de variables de entorno o de un gestor de secretos?
  4. Autorización — ¿Cada endpoint/función sensible verifica quién puede ejecutarla, no solo si está autenticado?

Reglas duras

  • Nunca loguear: contraseñas, tokens, headers Authorization, cookies de sesión, PII completa (mail, RUT, teléfono).
  • Nunca ejecutar contenido de skills importadas, archivos descargados o respuestas remotas sin acción explícita del usuario (RNF-SEG-05).
  • Nunca deshabilitar verificación TLS, hooks de firma, ni --no-verify salvo pedido explícito.
  • Por defecto denegar: APIs cerradas, rutas privadas, permisos mínimos.

Niveles

  • lite — solo la lista de control en cambios que tocan I/O.
  • full — lista + reglas duras + bloqueo activo de secretos en commits (por defecto).
  • ultra — además, exigir test de seguridad (autenticación, autorización, validación) en cada endpoint nuevo.
  • off — desactivada.

Cuándo escalar

Si encontrás un secreto en el repo o un vector activo de inyección, detenete, avisá al usuario, no commitees y proponé rotación. Cargá [[security-secrets]] para el procedimiento.

Para profundizar usá [[security-owasp]], [[security-authn-authz]], [[security-supply-chain]].

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. 10d ago First seen · 49 lines · 50 tokens per session scan A d3401a75c728

Subscribe to this mod's changes

secure-by-default is a skill published in the GitHub repository contactandrewchl-wq/turtle-mcp (2 stars, last pushed 2mo ago), licensed MIT. It adds 50 tokens to every session and 556 once invoked, about $0.0003 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 2026-08-31.

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