auditing-code-for-vulnerabilities

A source-code security review method for finding vulnerabilities, which are flaws attackers could exploit. It follows how untrusted data moves through a codebase and checks whether the code keeps its intended safety rules.

In plain words
What is it for?
Use it to review repositories, code changes, branches, pull requests, or a particular class of security bug, and to document audit coverage.
Why use it?
It helps distinguish real security bugs from scanner warnings and find flaws that simple pattern matching may miss.

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/evilfreelancer/secs/auditing-code-for-vulnerabilities
Any agent
npx skills add EvilFreelancer/secs --skill auditing-code-for-vulnerabilities
Clone the repo
git clone --depth 1 https://github.com/EvilFreelancer/secs

Made for: Claude Code, Codex.

Per session 67 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,042 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin 91% copy Near-identical to another mod 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 $0.00067 $0.03042
Opus 5 $0.00034 $0.01521
Sonnet 5 $0.00013 $0.00608
Haiku 4.5 $0.00007 $0.00304

Measured 2d ago against content hash fea4dd1a5db2, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

auditing-code-for-vulnerabilities scanned grade A 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 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.

Runs shell commandslowCapability

Expected in a hook, worth knowing in a rule or an instructions file.

rg -n 'os\.system|subprocess.*shell\s*=\s*True|child_process\.exec\(|execSync|Statement\.execute|\.raw\(|fmt\.Sprintf.*SELECT'
Origin

This is a copy

91% identical to auditing-code-for-vulnerabilities — 2 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.agents/skills/auditing-code-for-vulnerabilities/SKILL.md · 270 lines

How it starts

The opening of the file, as written. The whole thing — 270 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Auditing Code for Vulnerabilities

Finding real bugs in source code is a different job from running a scanner. A scanner matches patterns; an auditor builds a model of what the code is supposed to guarantee and then hunts for the paths where that guarantee breaks. This skill is the methodology for the second job.

When to Use

  • Auditing a repository, service, or library for security defects
  • Reviewing a diff, branch, or pull request for introduced vulnerabilities
  • Hunting for a specific bug class across a large codebase
  • Validating whether a scanner finding or a reported vulnerability is real
  • Building an audit plan and coverage report for a client engagement

When NOT to Use

  • Black-box testing of a running app — use testing-web-applications or testing-apis
  • A PHP codebase specifically — this methodology applies directly; watch for type juggling, unserialize/phar POP chains, and php:// wrappers
  • Hunting a planted webshell or backdoor rather than a vulnerability — use hunting-web-backdoors
  • Binary-only targets — use analyzing-binaries
  • Dependency and build-pipeline risk — use auditing-supply-chain
  • Cryptographic construction review — use reviewing-cryptography
  • Writing up finished findings — use reporting-security-findings
  • Running a multi-agent discovery campaign across a whole target with builder/critic separation and iteration — use orchestrating-vulnerability-research, which dispatches this skill as the per-slice hunter

The Loop

Auditing is four passes, not one. Do not skip to pass 3.

1. Context      → what does this system protect, and from whom?
2. Attack surface → where does untrusted input enter, and what does it reach?
3. Hunt          → trace specific bug classes along those paths
4. Verify        → prove exploitability before you write a word

Pass 1: Build context before reading code

Do not open files at random. Spend the first block of effort answering:

Read the full file on GitHub · 270 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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 · 270 lines · 67 tokens per session scan A fea4dd1a5db2

Subscribe to this mod's changes

auditing-code-for-vulnerabilities is a skill published in the GitHub repository EvilFreelancer/secs (10 stars, last pushed 23d ago), licensed Apache-2.0. It adds 67 tokens to every session and 3,042 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 1 finding (runs shell commands). It is 91% identical to auditing-code-for-vulnerabilities, differing in 2 lines, and is treated as a copy.

Related

Other skills, from other repositories

Blue Team Defense & Hardening

System hardening, detection engineering, security baseline monitoring, patch management, defense-in-depth architecture, and security posture improvement.

Masriyan/Claude-Code-CyberSecurity-Skill · 30 tokens

analyzing-email-headers-for-phishing-investigation

Parse and analyze email headers to trace the origin of phishing emails, verify sender authenticity, and identify spoofing through SPF, DKIM, and DMARC validation.

26zl/cybersec-toolkit · 44 tokens

analyzing-golang-malware-with-ghidra

Reverse engineer Go-compiled malware using Ghidra with specialized scripts for function recovery, string extraction, and type reconstruction in stripped Go binaries.

26zl/cybersec-toolkit · 40 tokens

analyzing-prefetch-files-for-execution-history

Parse Windows Prefetch files to determine program execution history including run counts, timestamps, and referenced files for forensic investigation.

26zl/cybersec-toolkit · 34 tokens

analyzing-ios-app-security-with-objection

Performs runtime mobile security exploration of iOS applications using Objection, a Frida-powered toolkit that enables security testers to interact with app internals without jailbreaking. Use when assessing iOS app security posture, bypassing client-side protections, dumping keychain items, inspecting filesystem…

26zl/cybersec-toolkit · 99 tokens

add-tool

Use when adding a new cybersecurity tool to this installer. Walks through editing the right module file, adding to toolsconfig.json, running validators, and syncing MCP server data if needed. Triggers on phrases like "add tool", "add ", "register a new tool", "include X in the installer".

26zl/cybersec-toolkit · 68 tokens