A lot of the file hosting/download services have very dodgy advertising practices. I scanned the hosting site and it doesn't report malware so you should be safe. A lot of those ads are intended to scare you into clicking through to something else.

Might be time to find a new hosting solution. Are there any copyright or redistribution issues with the templates? Who made them? Does anyone have a complete set? Somewhere like GitHub would be a much safer solution provided that sharing them doesn't breach the terms of use.