See details in support ticket:
Difficult to fix in an easy way, perhaps best left to the server side? From the client side I guess it would require ajax to check the file type.
I think if they are in an image tag we can assume that the URL points to an image, perhaps there is no need to do a file extension check in the client side scraper.
Mmm, ok. If we destroy the intertubes, on your head be it ;)
Fixed in a64e84a