Created attachment 7047 patch to use https imgur supports https uploading and xfce4-screenshooter should use https to do that. I have attached a very simple patch (just change http to https).
Andre Miranda referenced this bugreport in commit 462ccbc7113cd64771c1a37ad7d52ec050fe7974 Use HTTPS for imgur (Bug #13415) https://git.xfce.org/apps/xfce4-screenshooter/commit?id=462ccbc7113cd64771c1a37ad7d52ec050fe7974
Pushed to master, thanks!