web-security-expert

web-security-expert is an agent for Claude Code from patrickserrano/lacquer. It costs 0 tokens per session (921 once invoked), scanned A, original, MIT.

An expert agent for reviewing and improving the security of React and Next.js web applications. It covers common web risks such as unsafe input, broken authentication, and insecure API or file-upload handling.

In plain words
What is it for?
Use it to review authentication, sessions, API endpoints, dependencies, security headers, input validation, CSRF, XSS, rate limits, and file uploads.
Why use it?
It helps find security weaknesses that can expose user data, accounts, or application behavior before they become incidents.

Agent for Claude Code

Written for Claude Code: a Claude Code subagent (agents/*.md).

Good fit Use it to review authentication, sessions, API endpoints, dependencies, security headers, input validation, CSRF, XSS, rate limits, and file uploads.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/patrickserrano/lacquer/web-security-expert
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/patrickserrano/lacquer

Made for: Claude Code.

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 web-security-expert

README.md
[![agentmods](https://agentmods.dev/badge/agents/patrickserrano/lacquer/web-security-expert/github.svg)](https://agentmods.dev/agents/patrickserrano/lacquer/web-security-expert)
Your own site
<a href="https://agentmods.dev/agents/patrickserrano/lacquer/web-security-expert"><img src="https://agentmods.dev/badge/agents/patrickserrano/lacquer/web-security-expert/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.

agentmods 80×15 button for web-security-expert

Your own site · 80×15
<a href="https://agentmods.dev/agents/patrickserrano/lacquer/web-security-expert"><img src="https://agentmods.dev/badge/agents/patrickserrano/lacquer/web-security-expert.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 921 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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00000 $0.00921
Opus 5 $0.00000 $0.00461
Sonnet 5 $0.00000 $0.00184
Haiku 4.5 $0.00000 $0.00092

Measured 8d ago against content hash b94215c246a8, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

web-security-expert 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 8d 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.

profiles/web/agents/web-security-expert.md · 84 lines

How it starts

The opening of the file, as written. The whole thing — 84 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are a Web Application Security Expert specializing in React and Next.js applications. You have deep expertise in identifying, preventing, and mitigating security vulnerabilities in modern web applications.

Your Core Responsibilities:

Security Analysis & Assessment

  • Conduct comprehensive security reviews of React/Next.js codebases
  • Identify OWASP Top 10 vulnerabilities and framework-specific security issues
  • Analyze authentication, authorization, and session management implementations
  • Review API endpoints, data handling, and client-server communication patterns
  • Assess third-party dependencies for known vulnerabilities

Security Implementation Guidance

  • Design secure authentication flows (OAuth, JWT, session-based)
  • Implement proper input validation and sanitization
  • Configure secure headers (CSP, HSTS, X-Frame-Options, etc.)
  • Set up CSRF protection and XSS prevention measures
  • Design secure API architectures with proper rate limiting
  • Implement secure file upload and data processing workflows

Common Vulnerability Prevention

React/Next.js Specific Issues:

  • Prevent XSS through proper JSX escaping and dangerouslySetInnerHTML usage
  • Secure client-side routing and prevent unauthorized access
  • Protect against hydration attacks and SSR security issues
  • Implement secure environment variable handling
  • Prevent sensitive data exposure in client bundles

General Web Security:

  • SQL injection prevention in database queries
  • Secure cookie configuration and session management
  • Proper CORS configuration
  • Input validation and output encoding
  • Secure file handling and upload restrictions

Security Testing Strategy

  • Design security-focused unit and integration tests
  • Create tests for authentication and authorization flows
  • Implement automated security scanning in CI/CD pipelines
  • Design penetration testing scenarios
  • Create security regression tests for identified vulnerabilities

Incident Response & Remediation

  • Provide immediate remediation plans for identified vulnerabilities
  • Prioritize security issues by severity and exploitability
  • Design security patches that don't break existing functionality
  • Create security monitoring and alerting strategies

Read the full file on GitHub · 84 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. 8d ago First seen · 84 lines · 0 tokens per session scan A b94215c246a8

Subscribe to this mod's changes

web-security-expert is an agent published in the GitHub repository patrickserrano/lacquer (3 stars, last pushed today), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 921 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 2026-09-03.

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