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.
npx skills add kevinnft/ai-agent-skills --skill security-and-hardeninggit clone --depth 1 https://github.com/kevinnft/ai-agent-skillsWrote 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.
[](https://agentmods.dev/skills/kevinnft/ai-agent-skills/security-and-hardening)<a href="https://agentmods.dev/skills/kevinnft/ai-agent-skills/security-and-hardening"><img src="https://agentmods.dev/badge/skills/kevinnft/ai-agent-skills/security-and-hardening/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.
<a href="https://agentmods.dev/skills/kevinnft/ai-agent-skills/security-and-hardening"><img src="https://agentmods.dev/badge/skills/kevinnft/ai-agent-skills/security-and-hardening.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00048 | $0.02707 |
| Opus 5 | $0.00024 | $0.01354 |
| Sonnet 5 | $0.00010 | $0.00541 |
| Haiku 4.5 | $0.00005 | $0.00271 |
Grade A, and why
security-and-hardening 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.
This is a copy
92% identical to security-and-hardening — 5 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 355 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Security and Hardening
Overview
Security-first development practices for web applications. Treat every external input as hostile, every secret as sacred, and every authorization check as mandatory. Security isn't a phase — it's a constraint on every line of code that touches user data, authentication, or external systems.
When to Use
- Building anything that accepts user input
- Implementing authentication or authorization
- Storing or transmitting sensitive data
- Integrating with external APIs or services
- Adding file uploads, webhooks, or callbacks
- Handling payment or PII data
The Three-Tier Boundary System
Always Do (No Exceptions)
- Validate all external input at the system boundary (API routes, form handlers)
- Parameterize all database queries — never concatenate user input into SQL
- Encode output to prevent XSS (use framework auto-escaping, don't bypass it)
- Use HTTPS for all external communication
- Hash passwords with bcrypt/scrypt/argon2 (never store plaintext)
- Set security headers (CSP, HSTS, X-Frame-Options, X-Content-Type-Options)
- Use httpOnly, secure, sameSite cookies for sessions
- Run
npm audit(or equivalent) before every release
Ask First (Requires Human Approval)
- Adding new authentication flows or changing auth logic
- Storing new categories of sensitive data (PII, payment info)
- Adding new external service integrations
- Changing CORS configuration
- Adding file upload handlers
- Modifying rate limiting or throttling
- Granting elevated permissions or roles
Never Do
- Never commit secrets to version control (API keys, passwords, tokens)
- Never log sensitive data (passwords, tokens, full credit card numbers)
- Never trust client-side validation as a security boundary
- Never disable security headers for convenience
- Never use
eval()orinnerHTMLwith user-provided data - Never store sessions in client-accessible storage (localStorage for auth tokens)
- Never expose stack traces or internal error details to users
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.
- 12d ago First seen · 355 lines · 48 tokens per session scan A 8eafa9448016
security-and-hardening is a skill published in the GitHub repository kevinnft/ai-agent-skills (14 stars, last pushed 1mo ago), licensed MIT. It adds 48 tokens to every session and 2,707 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 92% identical to security-and-hardening, differing in 5 lines, and is treated as a copy.
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