Malicious Script appearing after activating this theme

After activating the Sento Pro 1.6.0 Theme I get a new source in the client side pages, pointing to a dropbox stored-script that executes the check for some website-names and does nothing at a first glance.

Switching off the theme fixes the issues (but breaks the website)

This a major security breach

The page I need help with: [log in to see the link]