vulnerability-analysis

A source-code security auditing skill for tracing untrusted input through a system to risky operations. It covers issues such as injection, authentication errors, unsafe file or command handling, memory problems, cryptography, concurrency, and dependency risks.

In plain words
What is it for?
Use it to review input handling, access control, file operations, command execution, deserialization, cryptography, concurrent code, and software supply chains.
Why use it?
It provides a systematic method for finding security flaws instead of checking only obvious entry points. The approach follows data across trust boundaries and evaluates whether protections can be bypassed.

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/jessefmoore/offensive-claude-code/vulnerability-analysis
Any agent
npx skills add jessefmoore/offensive-claude-code --skill vulnerability-analysis
Clone the repo
git clone --depth 1 https://github.com/jessefmoore/offensive-claude-code

Made for: Claude Code, Codex.

Per session 0 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,146 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 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 $0.00000 $0.01146
Opus 5 $0.00000 $0.00573
Sonnet 5 $0.00000 $0.00229
Haiku 4.5 $0.00000 $0.00115

Measured 2d ago against content hash 8e0219d1fd50, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

vulnerability-analysis scanned grade A with 0 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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/vulnerability-analysis/SKILL.md · 115 lines

How it starts

The opening of the file, as written. The whole thing — 115 lines — stays where its author put it; the contents beside it link to each section on GitHub.


name: vulnerability-analysis description: Expert-level source code security auditing — taint analysis, memory safety, injection classes, auth flaws, crypto weaknesses, concurrency bugs, supply chain risks metadata: type: offensive phase: analysis

Vulnerability Analysis

Every vulnerability you miss is one an attacker can find. Systematic analysis traces untrusted data from source to sink, evaluates filters for bypass, and questions every trust boundary assumption.

When to Activate

  • Reviewing any code for security vulnerabilities
  • Auditing authentication, authorization, or session logic
  • Evaluating input handling and output encoding
  • Assessing cryptographic implementations
  • Reviewing file operations, command execution, or deserialization
  • Checking for race conditions in concurrent code
  • Analyzing dependency security and supply chain risks

Core Methodology

Taint Analysis: Mark untrusted data at origin (source), track propagation to dangerous operations (sink). Vulnerability exists when tainted data reaches sink without adequate sanitization.

Source-Forward: Start from data entry points, trace every path to sinks. Comprehensive but time-consuming.

Sink-Backward: Start from dangerous operations (eval, exec, SQL, innerHTML), trace backward to sources. Faster and targeted.

Hybrid Approach: Sink-backward for rapid high-risk identification, then source-forward for complete coverage.

Rule Categories by Priority

Priority Category Impact
1 Taint Analysis CRITICAL
2 Memory Safety CRITICAL
3 Injection Attacks CRITICAL
4 Authentication & Authorization HIGH
5 Cryptographic Vulnerabilities HIGH
6 Concurrency & Race Conditions HIGH
7 Web & API Security MEDIUM-HIGH
8 Supply Chain & Dependencies MEDIUM

Audit Protocol

  1. Reconnaissance: Identify language, frameworks, trust boundaries, sensitive data, high-value targets. Establish threat model.
  2. Attack Surface Enumeration: Map all entry points — HTTP endpoints, CLI args, file inputs, IPC, deserialization points.
  3. Systematic Analysis: Apply hybrid taint analysis across all source-sink paths.
  4. False Positive Reduction:
    • Trace validation chains upstream — is the value bounded before reaching sink?
    • Confirm reachability — can attacker actually trigger this path?
    • Evaluate against threat model — does exploitation require capabilities attacker doesn't have?
    • Check for established patterns — recognized safe idioms in the domain?
  5. Exploitability Gate: Before reporting ANY finding:
    • Are you certain this isn't expected functionality?
    • Is this a valid vulnerability worth reporting?
    • Is it actually exploitable in production?
  6. Findings: Document CWE, severity, root cause, exploitation scenario, remediation.
  7. Variant Hunting: Generalize each finding into a pattern and search for variants.

Read the full file on GitHub · 115 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 · 115 lines · 0 tokens per session scan A 8e0219d1fd50

Subscribe to this mod's changes

vulnerability-analysis is a skill published in the GitHub repository jessefmoore/offensive-claude-code (2 stars, last pushed 3mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 1,146 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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