A TimThumb error has occured

The following error(s) occured:

You may not fetch images from that site. To enable this site in timthumb, you can either add it to $ALLOWED_SITES and set ALLOW_EXTERNAL=true. Or you can set ALLOW_ALL_EXTERNAL_SITES=true, depending on your security needs.

Query String : src=https://iacconference.org//images/interface/logo_index.png&w=100&h=100&zc=1&q=90
TimThumb version : 2.8.10