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 svngoku/coding-agents-skills --skill security-best-practicesgit clone --depth 1 https://github.com/svngoku/coding-agents-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/svngoku/coding-agents-skills/security-best-practices)<a href="https://agentmods.dev/skills/svngoku/coding-agents-skills/security-best-practices"><img src="https://agentmods.dev/badge/skills/svngoku/coding-agents-skills/security-best-practices/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/svngoku/coding-agents-skills/security-best-practices"><img src="https://agentmods.dev/badge/skills/svngoku/coding-agents-skills/security-best-practices.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 | $0.00174 | $0.04680 |
| Opus 5 | $0.00087 | $0.02340 |
| Sonnet 5 | $0.00035 | $0.00936 |
| Haiku 4.5 | $0.00017 | $0.00468 |
Grade B, and why
security-best-practices 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 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: scheme + host **allowlist**; forbid user-supplied URLs to internal services; block link-local (`169.254.169.254` metadata) and private ranges; disable redirects or re-validate each hop. 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.
| Python | `requests.get(user_url)` unchecked | SSRF | Scheme/host allowlist, block private IPs | Runs shell commandslowCapability
Expected in a hook, worth knowing in a rule or an instructions file.
os.system(f"ffmpeg -i {filename} out.mp4") How it starts
The opening of the file, as written. The whole thing — 298 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Security Best Practices
Review and harden application code against the vulnerabilities that actually get exploited: injection, broken authentication, IDOR, XSS, insecure secrets, weak dependencies. This skill is actionable engineering guidance, not a compliance checklist — each vulnerability class maps to a concrete code-level fix, with cheat-sheets for Python, JavaScript/TypeScript, and Go plus a worked secure-login example.
Quick Reference
| Topic | Reference |
|---|---|
| STRIDE worksheet, trust boundaries, least privilege, DFDs | threat-modeling.md |
| JWT verification, OAuth2 flows, OIDC, token storage | jwt-oauth.md |
Core Workflow
- Scope the review. List entry points (HTTP routes, message consumers, CLIs, file processors), sensitive data (PII, credentials, payment data), and trust boundaries. Note the languages/frameworks so the right cheat-sheet applies.
- Threat-model in 5 minutes. Run the STRIDE table below per entry point; mark high-risk flows (auth, uploads, deserialization, outbound HTTP). Full worksheet: threat-modeling.md.
- Walk the OWASP map. Check every applicable row in the table below. Most findings come from three rows: access control (IDOR), injection, and security misconfiguration.
- Verify secure defaults and apply the cheat-sheet. TLS, headers, CORS, cookies, non-leaky errors (Secure Defaults), then grep for your language's dangerous patterns (SQL f-strings, pickle, innerHTML, eval) and fix confirmed hits.
- Report findings. Prioritize by severity × likelihood; give
file:line, the vulnerability class, why it matters, and the fix. Offer to implement the fixes.
Threat Modeling in 5 Minutes
| Letter | Threat | Ask | Example | Typical fix |
|---|---|---|---|---|
| S | Spoofing | Can someone pretend to be another user/service? | Forged JWT, stolen session | Strong auth, signed tokens, verify identity |
| T | Tampering | Can data be modified in transit or at rest? | SQL injection, unsigned payloads | TLS, signatures/HMAC, parameterized queries |
| R | Repudiation | Can an action be denied after the fact? | "I never made that transfer" | Audit logs, signed receipts |
| I | Information disclosure | Can sensitive data leak? | Stack traces, IDOR, secrets in logs | Least privilege, redaction, generic errors |
| D | Denial of service | Can the service be overwhelmed? | Expensive queries, no rate limits | Rate limiting, resource limits, timeouts |
| E | Elevation of privilege | Can a user do more than allowed? | Role escalation, IDOR | Server-side authorization on every action |
What ships with it
8 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 · 298 lines · 174 tokens per session scan B bbf68e721958
security-best-practices is a skill published in the GitHub repository svngoku/coding-agents-skills (11 stars, last pushed 26d ago), licensed MIT. It adds 174 tokens to every session and 4,680 once invoked, about $0.0009 per session on Opus 5. A static security scan graded it B with 3 findings (cloud metadata endpoint, makes network calls, runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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