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 shennawardana23/skillme --skill security-and-hardeninggit clone --depth 1 https://github.com/shennawardana23/skillmeWrote 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/shennawardana23/skillme/security-and-hardening)<a href="https://agentmods.dev/skills/shennawardana23/skillme/security-and-hardening"><img src="https://agentmods.dev/badge/skills/shennawardana23/skillme/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/shennawardana23/skillme/security-and-hardening"><img src="https://agentmods.dev/badge/skills/shennawardana23/skillme/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 | $0.00087 | $0.02115 |
| Opus 5 | $0.00044 | $0.01058 |
| Sonnet 5 | $0.00017 | $0.00423 |
| Haiku 4.5 | $0.00009 | $0.00212 |
Grade B, and why
security-and-hardening scanned grade B with 1 finding 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 9d 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.
- **SSRF** — any server-side fetch of a user-influenced URL needs a host allowlist, a check that *every* resolved IP is a public unicast address, and `redirect: 'error'`. The `169.254.169.254` cloud metadata address is t Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.
How it starts
The opening of the file, as written. The whole thing — 101 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Security and Hardening
This is a build-time skill: it hardens a feature while it's being designed and written. For auditing code that already exists, use security-review (priority checklist) or security-analysis (pattern scan). Treat every external input as hostile, every secret as sacred, every authorization check as mandatory — security is a constraint on every line touching user data, auth, or external systems, not a phase at the end.
Process: threat model first
Controls bolted on without a threat model are guesses. Before writing hardening code, spend five minutes thinking like an attacker:
- Map the trust boundaries — where does untrusted data cross into the system? HTTP requests, form fields, file uploads, webhooks, third-party API responses, 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?" and make that the 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.
The three-tier boundary system
Always do (no exceptions): validate all external input at the boundary; parameterize every database query; encode output via framework auto-escaping; use HTTPS everywhere; hash passwords with bcrypt/scrypt/argon2; set security headers (CSP, HSTS, X-Frame-Options); use httpOnly/secure/sameSite cookies for sessions; run a dependency audit before every release.
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.
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.
- 9d ago First seen · 101 lines · 87 tokens per session scan B 5431dd1c68d9
security-and-hardening is a skill published in the GitHub repository shennawardana23/skillme (2 stars, last pushed 15d ago), licensed Apache-2.0. It adds 87 tokens to every session and 2,115 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it B with 1 finding (cloud metadata endpoint). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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hello-world
A minimal test skill that greets the user and demonstrates the ASM publish workflow.