THIRD PARTY IMAGE

Did you just upload it to the /wp-content/uploads/ or did you just like right click > copy?

I just use right clicks. And it works on my site https://www.i-sastera.com (v2.9.1) and site https://drirwan.wordpress.com (free WP website) though.

You need to use full (absolute) urls in WordPress.

but I just use right clicks on my sites drirwan.wordpress.com and https://www.i-sastera.com and it works!