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 NovaCode37/claude-security-skills --skill cors-auditorgit clone --depth 1 https://github.com/NovaCode37/claude-security-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/novacode37/claude-security-skills/cors-auditor)<a href="https://agentmods.dev/skills/novacode37/claude-security-skills/cors-auditor"><img src="https://agentmods.dev/badge/skills/novacode37/claude-security-skills/cors-auditor/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/novacode37/claude-security-skills/cors-auditor"><img src="https://agentmods.dev/badge/skills/novacode37/claude-security-skills/cors-auditor.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00089 | $0.00680 |
| Opus 5 | $0.00044 | $0.00340 |
| Sonnet 5 | $0.00018 | $0.00136 |
| Haiku 4.5 | $0.00009 | $0.00068 |
Grade A, and why
cors-auditor scanned grade A 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 yesterday.
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.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
stdlib `urllib` and sends a throwaway `Origin` header to detect origin How it starts
The opening of the file, as written. The whole thing — 68 lines — stays where its author put it; the contents beside it link to each section on GitHub.
CORS Misconfiguration Auditor
Inspects CORS response headers and reports exploitable misconfigurations with
fixes. The analysis core is pure and offline-testable; live probing uses only
stdlib urllib and sends a throwaway Origin header to detect origin
reflection.
When to use this skill
- "Audit the CORS configuration of https://api.example.com."
- "Is it safe that my API returns Access-Control-Allow-Origin: *?"
- "Does my server reflect any Origin back?"
What it checks
- Wildcard + credentials —
Allow-Origin: *withAllow-Credentials: true(cors-wildcard-credentials). - Reflected origin — server echoes the request Origin back
(
cors-reflected-origin); critical when combined with credentials. - Null origin —
Allow-Origin: null(cors-null-origin). - Wildcard origin —
Allow-Origin: *without credentials (cors-wildcard). - Credentialed CORS — informational note when credentials are enabled
(
cors-credentials-enabled). - Wildcard methods —
Allow-Methods: *(cors-methods-wildcard).
How to run it
# Live probe (sends a throwaway Origin to test reflection)
python skills/cors-auditor/auditor.py https://api.example.com
# Probe with a specific origin
python skills/cors-auditor/auditor.py https://api.example.com --origin https://evil.example
# Offline: audit a captured header block; pass --origin to test reflection
python skills/cors-auditor/auditor.py --headers-file resp.txt --origin https://evil.example
# Only fail CI on high/critical (hides the medium wildcard + info notes)
python skills/cors-auditor/auditor.py https://api.example.com --min-severity high
Exit codes: 0 clean · 1 findings reported · 2 fetch/usage error.
Every reported finding fails the build. The default reports everything down to
info (including cors-credentials-enabled); raise --min-severity to
low/medium/high to filter advisory notes out of both the report and the
exit code.
Recommended workflow for Claude
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.
- yesterday Changed · +6 lines f0fd49d31bf1
- 11d ago First seen · 62 lines · 89 tokens per session scan A 1646dc006d21
cors-auditor is a skill published in the GitHub repository NovaCode37/claude-security-skills (11 stars, last pushed 2d ago), licensed MIT. It adds 89 tokens to every session and 680 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 1 finding (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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