Requirements
- Target platform
- OpenClaw
- Install method
- Manual import
- Extraction
- Extract archive
- Prerequisites
- OpenClaw
- Primary doc
- SKILL.md
Configure Cross-Origin Resource Sharing correctly to avoid security issues and debugging pain.
Configure Cross-Origin Resource Sharing correctly to avoid security issues and debugging pain.
Hand the extracted package to your coding agent with a concrete install brief instead of figuring it out manually.
I downloaded a skill package from Yavira. Read SKILL.md from the extracted folder and install it by following the included instructions. Tell me what you changed and call out any manual steps you could not complete.
I downloaded an updated skill package from Yavira. Read SKILL.md from the extracted folder, compare it with my current installation, and upgrade it while preserving any custom configuration unless the package docs explicitly say otherwise. Summarize what changed and any follow-up checks I should run.
Any header except: Accept, Accept-Language, Content-Language, Content-Type (with restrictions) Content-Type other than: application/x-www-form-urlencoded, multipart/form-data, text/plain Methods: PUT, DELETE, PATCH, or any custom method ReadableStream in request body Event listeners on XMLHttpRequest.upload One trigger = preflight; simple requests skip OPTIONS entirely
Access-Control-Allow-Origin: * incompatible with credentials—must specify exact origin Access-Control-Allow-Credentials: true required for cookies/auth headers Fetch: credentials: 'include'; XHR: withCredentials = true Without credentials mode, cookies not sent even to same origin for cross-origin requests
* doesn't match subdomains—*.example.com is invalid, not a pattern Can't use * with credentials—specify origin dynamically from request Access-Control-Allow-Headers: * works in most browsers but not all—list explicitly for compatibility Access-Control-Expose-Headers: * same issue—list headers you need to expose
Check Origin header against allowlist—don't reflect blindly (security risk) Regex matching pitfall: example.com matches evilexample.com—anchor the pattern null origin: sandboxed iframes, file:// URLs—usually reject, never allow as trusted Missing Origin header: same-origin or non-browser client—handle explicitly
Always include Vary: Origin when response depends on origin—even if you allow only one Without Vary: CDN/proxy caches response for one origin, serves to others—breaks CORS Add Vary: Access-Control-Request-Headers, Access-Control-Request-Method for preflight caching correctness
By default, JS can only read: Cache-Control, Content-Language, Content-Type, Expires, Last-Modified, Pragma Custom headers invisible to JS unless listed in Access-Control-Expose-Headers X-Request-ID, X-RateLimit-*, etc. need explicit exposure—common oversight
Access-Control-Max-Age: 86400 caches preflight for 24h—reduces OPTIONS traffic significantly Chrome caps at 2 hours; Firefox at 24 hours—values above are silently reduced Cached per origin + URL + request characteristics—not globally Set to 0 or omit during development—caching hides config changes
CORS error in browser = request reached server and came back—check server logs Preflight failure: server must return 2xx with CORS headers on OPTIONS—404/500 = failure Opaque response in fetch: mode: 'no-cors' succeeds but response is empty—usually not what you want Network tab shows CORS errors; Console shows which header is missing
Only setting CORS headers on main handler, not OPTIONS—preflight fails Setting headers after error response—CORS headers missing on 4xx/5xx breaks error handling Proxy stripping headers—verify headers reach client, not just that server sets them Access-Control-Allow-Origin: "*", "https://example.com"—must be single value, not list
Don't reflect Origin header blindly—validate against allowlist first Private Network Access: Chrome requires Access-Control-Allow-Private-Network: true for localhost access from public web CORS doesn't prevent request from being sent—just blocks response reading; server still processes it Sensitive endpoints: don't rely on CORS alone; use authentication + CSRF tokens
Identity, auth, scanning, governance, audit, and operational guardrails.
Largest current source with strong distribution and engagement signals.