Detecting Command Injection Patterns

What it does

When your agent uses it

• : pre-commit gate on code that calls out to shell utilities
• Audit of file-processing / archive-handling / image-conversion code
• Shell=True with anything other than a fixed literal
• With: scan command injection

Example prompts

• “we shell out to a tool.”
• “scan command injection”
• “shell=True audit”
• “/detecting-command-injection-patterns”

Requirements

• Python 3
• Compatibility (from SKILL.md): Designed for Claude Code
• Pre-approved tools (allowed-tools): Read, Bash(python3:*), Glob, Grep

Workflow steps

3 steps, taken from the step headings in SKILL.md.

1. 1Run the scanner
2. 2Interpret findings
3. 3Remediation

What it can do on your machine

Read from SKILL.md and the folder at commit 23ea8d4. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves these tools, so the agent can use them without asking each time:

  • Read
  • Bash(python3:*)
  • Glob
  • Grep

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Ships 1 file in scripts/ (Python), which the agent can run.

  Shell commands in SKILL.md call:

  • python3
  • git

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

• Network

  No URLs in SKILL.md. Its commands use git, which can reach the network depending on how they are called.

  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.

• Compatibility

  Designed for Claude Code

  From compatibility in the SKILL.md frontmatter.

Context cost

Detecting Command Injection Patterns loads about 1.3k tokens when it runs, and up to ~4.8k if it reads all its reference files. Until then it costs about 224 tokens; SKILL.md has 343 words of instructions outside code blocks.

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

~224

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

~1.3k

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

~4.8k

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); the scripts in this folder are not scanned.

SKILL.md

The full file from jeremylongshore/tons-of-skills-marketplace at commit 23ea8d4, republished under its MIT licence (© jeremylongshore). 343 words, ~1,278 tokens.

name

detecting-command-injection-patterns

description

Scan a source tree for command-injection vulnerable patterns: shell=True calls in Python subprocess, os.system / os.popen with interpolated strings, Node child_process.exec with template literals, Ruby backticks / Kernel#system / Kernel#exec with interpolation, Go exec.Command with shell wrapping, PHP system / passthru / shell_exec / backticks with $-interpolation, Java Runtime.exec with concatenated args. Use when: pre-commit gate on code that calls out to shell utilities, audit of file-processing / archive-handling / image-conversion code, post-bug-report investigation for "we shell out to a tool." Threshold: any shell-invocation API called with a string that contains a variable interpolation, OR shell=True with anything other than a fixed literal. Trigger with: "scan command injection", "shell=True audit", "find exec calls", "check os.system".

allowed-tools

Read, Bash(python3:*), Glob, Grep

compatibility

Designed for Claude Code

disallowed-tools

Bash(rm:*), Bash(curl:*)

version

3.30.0

author

Jeremy Longshore <jeremy@intentsolutions.io>

license

MIT

tags

security, static-analysis, command-injection, pentest

python3 ${CLAUDE_PLUGIN_ROOT}/skills/detecting-command-injection-patterns/scripts/scan_cmdi.py /path/to/repo

Usage: scan_cmdi.py PATH [OPTIONS]

Options:
  --output FILE      Write findings to FILE
  --format FMT       json | jsonl | markdown (default: markdown)
  --min-severity SEV (default: info)
  --include-tests    Include test directories (default: excluded)
  --languages LIST   Comma-separated subset to scan

python3 ${CLAUDE_PLUGIN_ROOT}/skills/detecting-command-injection-patterns/scripts/scan_cmdi.py \
    --min-severity high $(git diff --name-only main...HEAD | tr '\n' ' ')

- name: Command-injection scan
  run: |
    python3 plugins/security/penetration-tester/skills/detecting-command-injection-patterns/scripts/scan_cmdi.py \
        . --min-severity high

© jeremylongshore, 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 3 other files (scripts, references) in skills/.curated/detecting-command-injection-patterns of jeremylongshore/tons-of-skills-marketplace.

• SKILL.md
• references/PLAYBOOK.md
• references/THEORY.md
• scripts/scan_cmdi.py

Open the folder on GitHubat commit 23ea8d4