home / skills / jeremylongshore / claude-code-plugins-plus-skills / cors-policy-validator

cors-policy-validator skill

safe

/skills/03-security-fundamentals/cors-policy-validator

This skill helps you implement and validate cors policy validators by providing step-by-step guidance, production-ready code, and security best practices.

npx playbooks add skill jeremylongshore/claude-code-plugins-plus-skills --skill cors-policy-validator

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SKILL.md

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---
name: "cors-policy-validator"
description: |
  Validate cors policy validator operations. Auto-activating skill for Security Fundamentals.
  Triggers on: cors policy validator, cors policy validator
  Part of the Security Fundamentals skill category. Use when working with cors policy validator functionality. Trigger with phrases like "cors policy validator", "cors validator", "cors".
allowed-tools: "Read, Write, Grep, Bash(npm:*)"
version: 1.0.0
license: MIT
author: "Jeremy Longshore <[email protected]>"
---

# Cors Policy Validator

## Overview

This skill provides automated assistance for cors policy validator tasks within the Security Fundamentals domain.

## When to Use

This skill activates automatically when you:
- Mention "cors policy validator" in your request
- Ask about cors policy validator patterns or best practices
- Need help with essential security skills covering authentication, input validation, secure coding practices, and basic vulnerability detection.

## Instructions

1. Provides step-by-step guidance for cors policy validator
2. Follows industry best practices and patterns
3. Generates production-ready code and configurations
4. Validates outputs against common standards

## Examples

**Example: Basic Usage**
Request: "Help me with cors policy validator"
Result: Provides step-by-step guidance and generates appropriate configurations


## Prerequisites

- Relevant development environment configured
- Access to necessary tools and services
- Basic understanding of security fundamentals concepts


## Output

- Generated configurations and code
- Best practice recommendations
- Validation results


## Error Handling

| Error | Cause | Solution |
|-------|-------|----------|
| Configuration invalid | Missing required fields | Check documentation for required parameters |
| Tool not found | Dependency not installed | Install required tools per prerequisites |
| Permission denied | Insufficient access | Verify credentials and permissions |


## Resources

- Official documentation for related tools
- Best practices guides
- Community examples and tutorials

## Related Skills

Part of the **Security Fundamentals** skill category.
Tags: security, authentication, validation, owasp, secure-coding

Overview

This skill automates validation and guidance for CORS policy configuration within Security Fundamentals. It helps generate secure CORS configurations, checks existing policies for common mistakes, and explains remediation steps. Use it to reduce CORS-related vulnerabilities and ensure safe cross-origin access patterns.

How this skill works

I inspect CORS policy definitions, headers, and runtime behaviors to detect overly permissive rules, wildcard leaks, and header misconfigurations. I produce corrected configuration snippets, explain security implications, and validate outputs against common standards and best practices. I also surface likely causes for failures and provide step-by-step remediation guidance.

When to use it

When you mention "cors policy validator", "cors validator", or "cors"
When reviewing CORS headers after deployment or during code reviews
When generating CORS configuration for APIs, web servers, or reverse proxies
When you suspect cross-origin security issues or inconsistent behavior across environments
During onboarding or security training to enforce safe CORS patterns

Best practices

Prefer explicit allowed origins over wildcards; list trusted domains
Restrict allowed methods and headers to the minimum required
Avoid Access-Control-Allow-Credentials with a wildcard origin; use explicit origins when credentials are needed
Validate and sanitize incoming Origin values before echoing them
Log and test CORS behavior in staging to catch environment-specific issues

Example use cases

Validate a server's Access-Control-Allow-* headers and receive corrected configuration snippets
Generate CORS settings for an API gateway, Nginx, or Express.js app with minimal privileges
Detect misconfigurations like Access-Control-Allow-Origin: * combined with credentials
Provide step-by-step remediation and tests to reproduce and verify fixes
Teach secure CORS patterns during security fundamentals training or onboarding

FAQ

What common CORS mistakes do you detect?

I detect wildcards used with credentials, overly broad allowed methods or headers, improper Origin echoing, and missing preflight handling for non-simple requests.

Can you generate code for specific servers?

Yes. I produce production-ready snippets for common platforms like Express.js, Nginx, and API gateways, tailored to the allowed origins, methods, and headers you specify.