Does this happen repeatedly? Checking out the Antarctic Output page didn't cause any output for me.
It was, toggling between all the games I have with steam workshop support, it was just killing floor that was making it happen - theres normally a few seconds between the game page load showing it has sworkshop and then loading the item - that was when this bug was triggering. The item doesn’t show as the highlighted mod now, so I cannot reproduce :/
Nothing extracted yet.
Visited the Killing Floor game page in my library, terminal spat out:
LoadTGA: Only type 2 and 10 targa RGB images supported
For what I think was the thumbnail for this content http://steamcommunity.com/sharedfiles/filedetails/?id=116332239