How to Test CORS Security with Claude
Test CORS configuration with Claude and ToolRouter. Find cross-origin security issues.
Tool
Claude transforms penetration testing into a conversational security review where each discovered vulnerability leads to deeper investigation. Ask Claude to scan your application, explain each finding in context, chain additional targeted tests based on initial results, and generate remediation code for every issue found. Its analytical depth is ideal for security-conscious developers who want to understand not just what is vulnerable but why and how to fix it permanently.
Connect ToolRouter to Claude
1Go to Settings → Connectors → Add custom connector
2Enter the details below and click Add
Name
ToolRouterURL
https://api.toolrouter.com/mcp3Done — works on Claude chat, desktop, and mobile
Steps
Once connected (see setup above), use the Pentest tool:
- Ask Claude: "Test the CORS configuration of my application using pentest" and provide the URL
- Claude sends cross-origin requests with various Origin headers and analyzes responses
- Review which origins are accepted and whether credentials are exposed
- Tighten CORS configuration to only allow trusted origins
Example Prompt
Try this with Claude using the Pentest tool
Test the CORS configuration at https://api.staging.myapp.com. Check if it reflects arbitrary origins, allows null origins, or exposes credentials to untrusted domains.
Tips
- Ask Claude to test with both legitimate and malicious Origin values
- Check CORS on every API endpoint -- some may have different configurations
- Ensure preflight responses are consistent with actual response headers