Did something changed in the uploading image via URL?
I'm often using Lunapic, online image editor. For cropping online images without download/upload etc. It's actor's portraits mostly. Upon processing I use temporary URL of the image in the editor to upload it. Yesterday everything was working fine. Today I can't upload any image from it. I'm getting Could not retrieve image from URL error. However I can open this URL in browser or download the image just fine.

