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 vanja-emichi/a0_agent_skills --skill security-and-hardeninggit clone --depth 1 https://github.com/vanja-emichi/a0_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/vanja-emichi/a0_agent_skills/security-and-hardening)<a href="https://agentmods.dev/skills/vanja-emichi/a0_agent_skills/security-and-hardening"><img src="https://agentmods.dev/badge/skills/vanja-emichi/a0_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/vanja-emichi/a0_agent_skills/security-and-hardening"><img src="https://agentmods.dev/badge/skills/vanja-emichi/a0_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 | $0.02787 |
| Opus 5 | $0.00024 | $0.01393 |
| Sonnet 5 | $0.00010 | $0.00557 |
| Haiku 4.5 | $0.00005 | $0.00279 |
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 11d 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
86% identical to security-and-hardening — 73 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 — 377 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Security and Hardening
Supporting files: This skill has a companion security checklist. Use
text_editor:readwith the full path shown in the file tree when this skill is loaded to opensecurity-checklist.md(sibling to this SKILL.md).
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) viacode_execution_toolbefore 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 ships with it
1 file 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.
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.
- 11d ago First seen · 377 lines · 48 tokens per session scan A 213b2427bb85
security-and-hardening is a skill published in the GitHub repository vanja-emichi/a0_agent_skills (5 stars, last pushed 1mo ago), licensed MIT. It adds 48 tokens to every session and 2,787 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 86% identical to security-and-hardening, differing in 73 lines, and is treated as a copy.
Other skills, from other repositories
007
Security audit, hardening, threat modeling (STRIDE/PASTA), Red/Blue Team, OWASP checks, code review, incident response, and infrastructure security for any project.
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API Security Testing
Comprehensive API security testing based on OWASP API Security Top 10 including broken authentication, injection attacks, rate limiting, BOLA/BFLA vulnerabilities, and automated security scanning with ZAP and custom scripts.
Web Application Security Testing
OWASP Top 10 testing, injection vulnerability detection, API security assessment, authentication testing, and web vulnerability reporting for authorized assessments.
security-patterns
Security patterns for authentication, defense-in-depth, input validation, OWASP Top 10, LLM safety, and PII masking. Use when implementing auth flows, security layers, input sanitization, vulnerability prevention, prompt injection defense, or data redaction.
security-expert
Expert-level application security, OWASP Top 10, penetration testing, and security best practices. Use when the user mentions OWASP, pentesting, appsec, vulnerability, encryption, or authentication, or when the task involves Security Principles, OWASP Top 10, Security Domains, or Broken Access Control.