I had the same issue. I added

Marzanna — Wed, 25 Jan 2017 15:15:40 +0000

I had the same issue. I added to my config:

custom_headers:
      "Access-Control-Allow-Origin": "*"
      "Access-Control-Allow-Methods": "GET, POST, PUT, OPTIONS, DELETE"
      "Access-Control-Allow-Headers": "Content-Type, Origin, X-Requested-With"

and it worked!

ejabberd - Comments for "http_upload cors problem with external web app"

I had the same issue. I added