# Send CORS to your agent Hand the extracted package to your coding agent with a concrete install brief instead of figuring it out manually. ## Fast path - Download the package from Yavira. - Extract it into a folder your agent can access. - Paste one of the prompts below and point your agent at the extracted folder. ## Suggested prompts ### New install ```text 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. ``` ### Upgrade existing ```text 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. ``` ## Machine-readable fields ```json { "schemaVersion": "1.0", "item": { "slug": "cors", "name": "CORS", "source": "tencent", "type": "skill", "category": "安全合规", "sourceUrl": "https://clawhub.ai/ivangdavila/cors", "canonicalUrl": "https://clawhub.ai/ivangdavila/cors", "targetPlatform": "OpenClaw" }, "install": { "downloadUrl": "/downloads/cors", "sourceDownloadUrl": "https://wry-manatee-359.convex.site/api/v1/download?slug=cors", "sourcePlatform": "tencent", "targetPlatform": "OpenClaw", "packageFormat": "ZIP package", "primaryDoc": "SKILL.md", "includedAssets": [ "SKILL.md" ], "downloadMode": "redirect", "sourceHealth": { "source": "tencent", "slug": "cors", "status": "healthy", "reason": "direct_download_ok", "recommendedAction": "download", "checkedAt": "2026-04-29T03:09:48.676Z", "expiresAt": "2026-05-06T03:09:48.676Z", "httpStatus": 200, "finalUrl": "https://wry-manatee-359.convex.site/api/v1/download?slug=cors", "contentType": "application/zip", "probeMethod": "head", "details": { "probeUrl": "https://wry-manatee-359.convex.site/api/v1/download?slug=cors", "contentDisposition": "attachment; filename=\"cors-1.0.0.zip\"", "redirectLocation": null, "bodySnippet": null, "slug": "cors" }, "scope": "item", "summary": "Item download looks usable.", "detail": "Yavira can redirect you to the upstream package for this item.", "primaryActionLabel": "Download for OpenClaw", "primaryActionHref": "/downloads/cors" }, "validation": { "installChecklist": [ "Use the Yavira download entry.", "Review SKILL.md after the package is downloaded.", "Confirm the extracted package contains the expected setup assets." ], "postInstallChecks": [ "Confirm the extracted package includes the expected docs or setup files.", "Validate the skill or prompts are available in your target agent workspace.", "Capture any manual follow-up steps the agent could not complete." ] } }, "links": { "detailUrl": "https://openagent3.xyz/skills/cors", "downloadUrl": "https://openagent3.xyz/downloads/cors", "agentUrl": "https://openagent3.xyz/skills/cors/agent", "manifestUrl": "https://openagent3.xyz/skills/cors/agent.json", "briefUrl": "https://openagent3.xyz/skills/cors/agent.md" } } ``` ## Documentation ### Preflight Triggers 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 ### Credentials Mode 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 ### Wildcard Limitations * 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 ### Origin Validation 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 ### Vary Header (Critical) 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 ### Exposed Headers 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 ### Preflight Caching 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 ### Debugging 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 ### Common Server Mistakes 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 ### Security 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 ## Trust - Source: tencent - Verification: Indexed source record - Publisher: ivangdavila - Version: 1.0.0 ## Source health - Status: healthy - Item download looks usable. - Yavira can redirect you to the upstream package for this item. - Health scope: item - Reason: direct_download_ok - Checked at: 2026-04-29T03:09:48.676Z - Expires at: 2026-05-06T03:09:48.676Z - Recommended action: Download for OpenClaw ## Links - [Detail page](https://openagent3.xyz/skills/cors) - [Send to Agent page](https://openagent3.xyz/skills/cors/agent) - [JSON manifest](https://openagent3.xyz/skills/cors/agent.json) - [Markdown brief](https://openagent3.xyz/skills/cors/agent.md) - [Download page](https://openagent3.xyz/downloads/cors)