IIS hijacks CORS Preflight OPTIONS request

Question

I am making a CORS POST request and setting the Content-Type header to json. This triggers a Preflight OPTIONS request to fire (this is good and expected)

This OPTIO

Answer 1

Check if URLScan tool is installed on IIS. When so check following section:

;
; The verbs (aka HTTP methods) listed here are those commonly
; processed by a typical IIS server.
;
; Note that these entries are effective if "UseAllowVerbs=1"
; is set in the [Options] section above.
;

GET
HEAD
POST
OPTIONS