security-review

security-review is a skill for Claude Code from haabe/mycelium. It costs 24 tokens per session (1,670 once invoked), scanned B, original, MIT.

A security review based on OWASP secure-design guidance, covering common weaknesses in code and system architecture.

In plain words
What is it for?
Reviewing validation, authentication, authorization, data protection, encryption, rate limits, browser security, and software supply-chain risks.
Why use it?
It helps find risks such as missing access checks, unsafe input handling, exposed secrets, weak encryption, and insecure configuration.

Skill for Claude Code

Written for Claude Code: ${CLAUDE_PLUGIN_ROOT} variable.

Runs only inside its plugin — its command needs a path that Claude Code sets for a plugin’s own hooks and for nothing else. Install the plugin, not this.

Part of the mycelium plugin — 61 skills, 6 hooks shipped together

Install

Getting it into your agent

This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.

Claude Code
/plugin marketplace add haabe/mycelium
Claude Code
/plugin install mycelium

Made for: Claude Code.

Or install mycelium, the plugin that ships this one along with the rest of its 61 skills, 6 hooks.

Wrote 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.

agentmods badge for security-review

README.md
[![agentmods](https://agentmods.dev/badge/skills/haabe/mycelium/security-review.svg)](https://agentmods.dev/skills/haabe/mycelium/security-review)
Your own site
<a href="https://agentmods.dev/skills/haabe/mycelium/security-review"><img src="https://agentmods.dev/badge/skills/haabe/mycelium/security-review.svg" alt="Measured on agentmods" height="20"></a>
Per session 24 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,670 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 1 finding. 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 5.1 $0.00024 $0.01670
Opus 5 $0.00012 $0.00835
Sonnet 5 $0.00005 $0.00334
Haiku 4.5 $0.00002 $0.00167

Measured 6d ago against content hash d85ded3cd720, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade B, and why

security-review scanned grade B 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 6d 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.

Instruction-override phrasingmediumPrompt injection

Text telling the model to disregard its earlier instructions or safety rules is the shape of a prompt injection, whoever wrote it.

- [ ] **LLM01 Prompt Injection**: User input (direct or indirect) cannot override system instructions

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

plugins/mycelium/skills/security-review/SKILL.md · 121 lines

How it starts

The opening of the file, as written. The whole thing — 121 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Security Review

Language-agnostic security review based on OWASP Secure by Design.

Checklist (OWASP Top 10:2025)

Updated to OWASP Top 10:2025 (released January 2025). Previous 2021 edition had different groupings.

A01:2025 — Broken Access Control

  • Least privilege enforced (users get minimum permissions needed)
  • Authorization checked on EVERY request (not just the first)
  • CORS restrictive (not *)
  • Directory listing disabled
  • Rate limiting on API/controller access

A02:2025 — Cryptographic Failures

  • Data encrypted at rest and in transit (TLS 1.2+)
  • No secrets in code, logs, or error messages
  • PII identified and classified in threat model
  • Passwords hashed with bcrypt/argon2 (never MD5/SHA1)
  • Cryptographic algorithms current (no deprecated ciphers)

A03:2025 — Injection

  • All user input validated (type, length, range, format)
  • Parameterized queries for ALL data access (never string concatenation)
  • Input allowlisting preferred over denylisting
  • Output encoded based on context (HTML, JS, URL, CSS — covers XSS)
  • Content Security Policy configured

A03b:2025 — Software Supply Chain Failures (new in 2025)

  • SBOM (Software Bill of Materials) maintained for critical dependencies
  • Build integrity verified (reproducible builds, signed artifacts)
  • Dependency provenance checked (not just version, but source authenticity)
  • Transitive dependencies audited (not just direct)
  • Lock files committed and verified

A04:2025 — Insecure Design

  • Threat modeling performed (STRIDE — see /mycelium:threat-model)
  • Secure design patterns used (defense in depth, fail secure)
  • Business logic abuse cases considered
  • Security requirements defined alongside functional requirements

A05:2025 — Security Misconfiguration

  • Default credentials changed
  • Unnecessary features/ports disabled
  • Security headers set (CSP, HSTS, X-Frame-Options, X-Content-Type-Options)
  • Error handling does not expose stack traces

Read the full file on GitHub · 121 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. 6d ago First seen · 121 lines · 24 tokens per session scan B d85ded3cd720

Subscribe to this mod's changes

security-review is a skill published in the GitHub repository haabe/mycelium (45 stars, last pushed yesterday), licensed MIT. It adds 24 tokens to every session and 1,670 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it B with 1 finding (instruction-override phrasing). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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