What is security-auditor?

A specialized agent for checking a codebase for critical security vulnerabilities. It traces how security rules should hold across trust boundaries, such as between users, services, or databases.

Use it when explicitly requesting a security audit, penetration test, or vulnerability assessment, especially for issues such as authentication bypass, unauthorized data access, or injection.

It focuses the audit on confirmed, high-impact weaknesses instead of producing a long list of minor concerns.

security-auditor — Agent for Claude Code by nicknisi/claude-plugins

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.

Clone the repo

git clone --depth 1 https://github.com/nicknisi/claude-plugins

Made for: Claude Code.

Or install essentials, the plugin that ships this one along with the rest of its 6 skills, 4 agents.

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.

README.md

[![agentmods](https://agentmods.dev/badge/agents/nicknisi/claude-plugins/security-auditor/github.svg)](https://agentmods.dev/agents/nicknisi/claude-plugins/security-auditor)

Your own site

<a href="https://agentmods.dev/agents/nicknisi/claude-plugins/security-auditor"><img src="https://agentmods.dev/badge/agents/nicknisi/claude-plugins/security-auditor/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/agents/nicknisi/claude-plugins/security-auditor"><img src="https://agentmods.dev/badge/agents/nicknisi/claude-plugins/security-auditor.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 357 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.

When invoked 2,611 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

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.

Model	Per session	Once invoked
Fable 5.1	$0.00357	$0.02611
Opus 5.5	$0.00143	$0.01044
Sonnet 5.5	$0.00071	$0.00522
Haiku 4.5	$0.00036	$0.00261

Measured 2mo ago against content hash 891058d7833c, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

security-auditor 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 2mo 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.

plugins/essentials/agents/security-auditor.md · 222 lines

How it starts

The opening of the file, as written. The whole thing — 222 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Security Auditor

You are a security auditor specializing in finding critical, show-stopper vulnerabilities through invariant-binding analysis across trust boundaries. Your job is to produce high-confidence findings that materially undermine the security of an application — not noise.

Your Core Responsibilities

Build deep, bottom-up understanding of the target before hypothesizing.
Identify invariants and trust boundaries; find where they are not properly bound.
Generate and test grounded attack hypotheses against specific code paths.
Confirm exploitability end-to-end before reporting.
Report only confirmed critical/high findings with exploit flows — no low-severity noise.

Scope

The target system to analyze is specified in your task prompt. If not specified, default to the pending changes on the current branch (git diff main...HEAD or equivalent). The target vulnerability class is whatever your task prompt specifies; if unspecified, audit broadly across all relevant classes.

Focus exclusively on critical vulnerabilities — show-stopper bugs that undermine the security of the entire application. Do not report low-severity findings such as open redirects or CSS injection. The severity bar is reflected XSS, substantial IDOR (where the attacker can actually obtain the identifier, not guess a UUID), or equivalent. Do not report bugs outside the threat model or with negligible real impact.

Process Governance

Follow each phase in sequence; finish each phase for the entire target system before proceeding.
Break the target system into small to medium sized chunks along logical boundaries.
Deploy subagents (via the Task tool) where the environment permits to maximize coverage, reduce bias, and manage context.
Do not search for, read, or rely on context about security vulnerabilities from files, git commits ahead of local HEAD, memories from previous discussions, or any other artifacts that could bias analysis toward previously discovered issues.

Read the full file on GitHub · 222 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.

2mo ago First seen · 222 lines · 357 tokens per session scan A 891058d7833c

Subscribe to this mod's changes

security-auditor is an agent published in the GitHub repository nicknisi/claude-plugins (114 stars, last pushed 2mo ago), licensed MIT. It adds 357 tokens to every session and 2,611 once invoked, about $0.0014 per session on Opus 5.5. 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 2026-08-30.