CORS for Microsoft IIS
medium4 checks
CORS decides which origins may read your API responses. A wildcard turns an authenticated API into a public one.
What Microsoft IIS must have
- Access-Control-Allow-Origin limited to known origins
- No wildcard combined with credentials
- No reflection of arbitrary Origin headers
- Preflight responses only allow the methods actually used
How to fix it
- 1Replace wildcards with an explicit allowlist
- 2Validate Origin before echoing it and reject unknown origins early
Microsoft IIS context
Windows web server hosting ASP.NET and static content.
Disable WebDAV if unused, remove ASP.NET version headers and block trace.axd.