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 agentmods add skills/hellotern/sextant/securitynpx skills add hellotern/Sextant --skill securitygit clone --depth 1 https://github.com/hellotern/SextantWhat 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 | $0.00131 | $0.01984 |
| Opus 5 | $0.00066 | $0.00992 |
| Sonnet 5 | $0.00026 | $0.00397 |
| Haiku 4.5 | $0.00013 | $0.00198 |
Grade A, and why
security 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 2d 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.
How it starts
The opening of the file, as written. The whole thing — 170 lines — stays where its author put it; the contents beside it link to each section on GitHub.
!../principles/SKILL_BODY.md
!../tool-gitnexus/SKILL_BODY.md
Security Audit Workflow
Core Principle
Security vulnerabilities are architectural violations in disguise: injection attacks are layer violations (untrusted data reaching logic without sanitization at the entry boundary); privilege escalation is an SRP violation (authorization logic entangled with business logic); secret leakage is a hidden dependency violation (credentials embedded in code rather than injected from outside). Fixing the architecture fixes the vulnerability.
Limitation declaration: This skill performs static code pattern analysis. It cannot execute
npm audit,pip-audit,bandit,semgrep,trivy, or any other automated scanner. The dependency findings in Dimension 4 are a preliminary review — they do not substitute for running real tooling.
Audit Dimensions
Progress tracking: At the start of each dimension, output an updated progress block.
Security Audit Progress ✓ Dimension 1: Input Validation — <Pass / Issues ⚠️ (N gaps)> → Dimension 2: Auth & Authorization — in progress ○ Dimension 3: Sensitive Data ○ Dimension 4: DependenciesReplace
○with→for the current dimension, and✓once complete.
Dimension 1: Input Validation
Scope: All public interfaces, API endpoints, and externally-controlled input paths.
| Check | Pass condition |
|---|---|
| Entry-layer validation | All external parameters (request body, query string, headers, file uploads) are validated before entering the logic layer |
| SQL parameterization | SQL is built with parameterized queries / prepared statements — never string concatenation |
| HTML output escaping | All user-controlled data is escaped before rendering in HTML (XSS prevention) |
| Shell command safety | Shell invocations use argument arrays, not string interpolation of user input |
| Path canonicalization | File paths are resolved (os.path.realpath() / .resolve()) before use to prevent path traversal |
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.
- 2d ago First seen · 170 lines · 131 tokens per session scan A b9ec3d89a533
security is a skill published in the GitHub repository hellotern/Sextant (15 stars, last pushed 4mo ago), licensed MIT. It adds 131 tokens to every session and 1,984 once invoked, about $0.0007 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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