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 skillmds/skillmd --skill security-and-hardeninggit clone --depth 1 https://github.com/skillmds/skillmdWrote 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/skillmds/skillmd/security-and-hardening)<a href="https://agentmods.dev/skills/skillmds/skillmd/security-and-hardening"><img src="https://agentmods.dev/badge/skills/skillmds/skillmd/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/skillmds/skillmd/security-and-hardening"><img src="https://agentmods.dev/badge/skills/skillmds/skillmd/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 | $0.04451 |
| Opus 5.5 | $0.00019 | $0.01780 |
| Sonnet 5.5 | $0.00010 | $0.00890 |
| Haiku 4.5 | $0.00005 | $0.00445 |
Grade B, and why
security-and-hardening scanned grade B with 3 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 1mo 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.
Cloud metadata endpointmediumServer-side request forgery
One request to 169.254.169.254 can return temporary IAM credentials.
The `range() !== 'unicast'` check covers loopback, link-local `169.254.169.254` (cloud metadata, the #1 SSRF target), private, and unique-local ranges across IPv4 and IPv6. Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.
Unrestricted tool accesslowExcessive agency
A wildcard tool grant or "run any command" leaves no least-privilege boundary at all.
- **Be wary of `postinstall` scripts** in unfamiliar packages — they run arbitrary code at install time. Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
await fetch(req.body.webhookUrl); This is a copy
92% identical to security-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 — 463 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
Process: Threat Model First
Controls bolted on without a threat model are guesses. Before hardening, spend five minutes thinking like an attacker:
- Map the trust boundaries. Where does untrusted data cross into your system? HTTP requests, form fields, file uploads, webhooks, third-party APIs, message queues, and LLM output. Every boundary is attack surface.
- Name the assets. What's worth stealing or breaking? Credentials, PII, payment data, admin actions, money movement.
- Run STRIDE over each boundary — a quick lens, not a ceremony:
| Threat | Ask | Typical mitigation |
|---|---|---|
| Spoofing | Can someone impersonate a user/service? | Authentication, signature verification |
| Tampering | Can data be altered in transit or at rest? | Integrity checks, parameterized queries, HTTPS |
| Repudiation | Can an action be denied later? | Audit logging of security events |
| Information disclosure | Can data leak? | Encryption, field allowlists, generic errors |
| Denial of service | Can it be overwhelmed? | Rate limiting, input size caps, timeouts |
| Elevation of privilege | Can a user gain rights they shouldn't? | Authorization checks, least privilege |
- Write abuse cases next to use cases. For each feature, ask "how would I misuse this?" — then make that your first test.
If you can't name the trust boundaries for a feature, you're not ready to secure it. This is OWASP A04: Insecure Design — most breaches begin in design, not code.
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.
- 1mo ago First seen · 463 lines · 48 tokens per session scan B 6b18a4367eed
security-and-hardening is a skill published in the GitHub repository skillmds/skillmd (143 stars, last pushed 4d ago), licensed MIT. It adds 48 tokens to every session and 4,451 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it B with 3 findings (cloud metadata endpoint, unrestricted tool access, makes network calls). It is 92% identical to security-hardening, differing in 5 lines, and is treated as a copy.
security-and-hardening compared with skills from other repositories
| Mod | Type | Stars | Last push | Licence | Scan | Tokens | Works with |
|---|---|---|---|---|---|---|---|
| security-and-hardeningskillmds/skillmd | Skill | 143 | 4d ago | MIT | B | 48 | Claude Code |
| sloplessberelevant-ai/slopless | Skill | 339 | 3d ago | MIT | A | 40 | Claude Code, Codex |
| suikonwiizo/suiko | Skill | 115 | yesterday | MIT | A | 192 | Codex |
| poly-lint-and-formatGoldziher/poly | Skill | 20 | today | MIT | A | 42 | Claude Code |
| poly-orchestratorGoldziher/poly | Skill | 20 | today | MIT | A | 43 | Claude Code |
| poly-mcpGoldziher/poly | Skill | 20 | today | MIT | A | 38 | Claude Code |
| poly-tiers-and-scopeGoldziher/poly | Skill | 20 | today | MIT | A | 60 | Claude Code |