security

A security review guide for Claude Code plugins and their executable parts, including scripts, hooks, package files, and MCP server configurations. It also covers supply-chain risks, data leaks, and prompt-injection patterns.

In plain words
What is it for?
Use it to audit plugins, MCP configurations, hooks, scripts, and other extension files for security risks.
Why use it?
It helps identify unsafe code or configuration before an extension is installed or allowed to run.

Skill for Claude CodeCodex

Install

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.

agentmods
npx agentmods add skills/xiaolai/nlpm/security
Any agent
npx skills add xiaolai/nlpm --skill security
Clone the repo
git clone --depth 1 https://github.com/xiaolai/nlpm

Made for: Claude Code, Codex.

Per session 53 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,161 The whole file, excluding the scripts and references it only reads on demand.
Security scan C 3 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00053 $0.04161
Opus 5 $0.00026 $0.02080
Sonnet 5 $0.00011 $0.00832
Haiku 4.5 $0.00005 $0.00416

Measured 2d ago against content hash ac3f6e0ef9c9, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade C, and why

security scanned grade C with 3 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.

Downloads and executes remote codemediumSupply chain

curl | sh runs whatever the server returns today, which is not necessarily what it returned when this was reviewed.

Patterns in `.md` files are instructional content, not executable code. A `curl | bash` in a README documents a user action the reader types manually — the plugin never runs it. Apply this rule universally:

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

Encoded or obfuscated payloadmediumSupply chain

base64 or hex that is decoded and executed hides what actually runs from anyone reading the file.

- Match `base64 -d | sh`, `base64.decode(...) | exec` only when the

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.

Patterns in `.md` files are instructional content, not executable code. A `curl | bash` in a README documents a user action the reader types manually — the plugin never runs it. Apply this rule universally:
codex/skills/security/SKILL.md · 321 lines

How it starts

The opening of the file, as written. The whole thing — 321 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Security Scan Patterns for Claude Code Plugins

Context-Aware File Classification

Before assigning severity to any finding, classify the file by its execution context:

File Type Examples Can Execute? Rule
Shell scripts *.sh, *.bash Yes Apply full severity table
Code files *.py, *.js, *.mjs, *.ts Yes Apply full severity table
Hook definitions hooks/hooks.json Runs on every tool call Apply full severity table
MCP configs .mcp.json Yes (server launch) Apply full severity table
Package manifests package.json Via npm scripts Apply full severity table
Documentation *.md (SKILL.md, CLAUDE.md, README.md) No Cap at Low — see rule below

Documentation Files (*.md)

Patterns in .md files are instructional content, not executable code. A curl | bash in a README documents a user action the reader types manually — the plugin never runs it. Apply this rule universally:

Any Critical or High pattern found in a .md file → downgrade to Low (informational). Note it as "instructional content in documentation — not executable."

Examples:

  • curl https://... | bash in README.md → Low: install instruction for end users
  • eval $var in SKILL.md → Low: pattern shown as example to avoid
  • new Function(...) in CLAUDE.md → Low: educational reference

Exception: if a .md file is explicitly referenced as a script via command: in hooks.json or executed via bash file.md, treat it as executable and apply full severity.

Scanning Workflow

  1. Classify files — categorize each file by execution context (see table above)
  2. Identify execution surfaces — map hooks, scripts, MCP configs, commands, and install scripts
  3. Scan each surface — apply pattern tables below, matching regex against file contents
  4. Apply context adjustments — downgrade documentation findings to Low per the markdown rule
  5. Validate findings — verify each Critical/High finding is in an executable context before finalizing
  6. Generate report — produce the structured report (see Report Format section)

Read the full file on GitHub · 321 lines

Changes

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.

  1. 2d ago First seen · 321 lines · 53 tokens per session scan C ac3f6e0ef9c9

Subscribe to this mod's changes

security is a skill published in the GitHub repository xiaolai/nlpm (133 stars, last pushed 2d ago), licensed ISC. It adds 53 tokens to every session and 4,161 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it C with 3 findings (downloads and executes remote code, encoded or obfuscated payload, 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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