location /static with alias /var/www/static/ looks harmless, but /static../ then reads files outside the folder. This skill finds that classic nginx bug and nine other risky settings, and tells you how to fix each one.

Your agent runs a scanner on nginx.conf, conf.d and sites-enabled files. Files are checked together and include lines inside the scanned folder are followed, using nginx's real add_header inheritance rules. It returns BLOCK, REVIEW, or NOT FLAGGED, with the file, line, reason, and a safer approach.

What it checks

BLOCK (fix before shipping)

• W01: autoindex on

• W02: SSLv3, TLS 1.0 or TLS 1.1 allowed

• W03: the alias off-by-slash path traversal

• W04: proxy_pass to a host taken from the request

REVIEW (check before release)

• W11: server_tokens not turned off

• W12: an HTTPS server without HSTS

• W13: weak ciphers such as RC4 or 3DES

• W14: client_max_body_size 0

• W15: no nosniff and framing headers

• W16: stub_status with no deny rule

What's included

• The scanner (Python 3.9+, standard library only)

• A rules guide with the reason and safer approach for each rule

• A risky and a safe example config, and the real report the scanner produces on the risky one

Limits

It reads config text. It does not follow includes outside the scanned folder, and it cannot see TLS settings on a load balancer or CDN in front of nginx. NOT FLAGGED is not a guarantee.

Contents

One ZIP file with 7 files: SKILL.md, the scanner in scripts/ (2 Python files), references/rules.md (every rule with its reason and safer approach), and examples/ (2 example files plus report.md, the real scanner output on the risky example).

How to use: This is an agent skill: a folder with a SKILL.md file and Python scripts that an AI coding agent such as Claude Code, Cursor, or Codex CLI can run. Unzip it into your agent's skills folder (for Claude Code: ~/.claude/skills/), then ask your agent to check your project. The scripts also run on their own with Python 3.9 or newer, with nothing to install. They read your files only: no network access, and nothing is sent anywhere.