Security Guidance

What it does

When your agent uses it

• You want a safety net during Claude Code sessions that touch security-sensitive code (auth
• User input handling
• — add security hook
• Block unsafe code

Example prompts

• “add security hook”
• “block unsafe code”
• “detect command injection before write”
• “/security-guidance”

Requirements

• Python 3
• Node.js

Workflow steps

6 steps, taken from the first numbered list in SKILL.md.

1. 1Claude Code is about to run Edit, Write, or MultiEdit
2. 2PreToolUse hook fires → invokes security_reminder_hook.py with the tool input as JSON on stdin
3. 3The hook extracts file_path + content + checks against the pattern table
4. 4If a pattern matches AND this warning hasn't been shown for this file+rule in this session
5. 5If a pattern matches BUT the warning was already shown this session
6. 6If no pattern matches

What it can do on your machine

Read from SKILL.md and the folder at commit 19392f7. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Shell commands in SKILL.md call:

  • claude

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • github.com

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Security Guidance loads about 1.9k tokens when it runs, and up to ~4k if it reads all its reference files. Until then it costs about 205 tokens; SKILL.md has 770 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~205

When it runs · the whole SKILL.md, loaded when a task matches

~1.9k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~4k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from alirezarezvani/claude-skills at commit 19392f7, republished under its MIT licence (© alirezarezvani). 770 words, ~1,945 tokens.

name

security-guidance

description

PreToolUse security-anti-pattern hook for Claude Code. Catches 12 common security risks (command injection, XSS, SQL injection, unsafe deserialization, GitHub Actions workflow injection, eval/new Function code injection) BEFORE the Edit/Write/MultiEdit operation completes. Session-state caching prevents duplicate warnings on the same file+rule combo. Stdlib only — no dependencies. Use when you want a safety net during Claude Code sessions that touch security-sensitive code (auth, payments, user input handling, IaC). Disable with ENABLE_SECURITY_REMINDER=0 if you need to perform a verified-safe operation that would otherwise trip a pattern. Triggers — "add security hook", "block unsafe code", "detect command injection before write", "prevent SQL injection patterns", "security warning hook".

# In Claude Code:
/plugin marketplace add alirezarezvani/claude-skills
/plugin install security-guidance@claude-code-skills

ENABLE_SECURITY_REMINDER=0 claude
# Hook is bypassed for this session

# SAFETY: pickle is the required serialization format for this internal tool.
# This file does NOT accept untrusted input. See SECURITY.md for boundary analysis.
import pickle

tail -f ~/.claude/security-warnings-log.txt
# Shows JSON decode errors, state-file save failures, etc.

© alirezarezvani, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 1 other file (references) in engineering/security-guidance/skills/security-guidance of alirezarezvani/claude-skills.

• SKILL.md
• references/pretooluse_hook_canon.md

Open the folder on GitHubat commit 19392f7