title: No 'Access-Control-Allow-Origin' header is present on the requested resource for azure web app
body: <p>I'm getting this error when I try to access azure web app(rest api) from a react app. </p>
  
  <p>I modified web apps core to accept CORE origins from "*", but getting same error. But if I disable "Authentication / Authorization" option of azure web app then there is no errors like this. This only happens if I enabled "Authentication / Authorization" with an Azure AD app.</p>
  
  <p>**Access to fetch at '<a href="https://login.windows.net/XXXXXX/oauth2/authorize?response_type=id_token&amp;redirect_uri=XXXXX" rel="nofollow noreferrer">https://login.windows.net/XXXXXX/oauth2/authorize?response_type=id_token&amp;redirect_uri=XXXXX</a>' (redirected from '<a href="https://AAAwebapp.azurewebsites.net/XXXXX" rel="nofollow noreferrer">https://AAAwebapp.azurewebsites.net/XXXXX</a>') from origin 'null' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.*</p>