Rated 1 out of 5 stars

After install on FF 36.0 Whois Lookup & ... appeared correctly in the add-ons list, but does nothing. At least nothing you would exspect like adding a button to your add-on-bar or an option to the context menu. So, in my case it provided no function, nothing useful, just nothing.
What it did, as I realized watching the HTTP response headers, was excessive spying. Each and every page I visited.was instantly phoned home (home to Key Systems, Germany, who are hiding behind the "myip.ms" profile. For whatever reason.) and sent to Google Analytics - together with a suspiciously long, encrypted parameter list.
So to put this in clear words: This plugin does not just send queries about websites, you want examined, it sends everything you do to Key Systems AG as well as to Google Analytics. I, for one, would not exactly call this "moderate use".