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 : w=640&h=320&zc=2&src=https://www.butobu.rs/members/butobu_images/im_1111852141547460826.jpg
TimThumb version : 2.8.13