The link got me V 184.108.40.206 [based on version shown under options/ settings/about...and the "not signed" warning is gone under add-ons On this PC probably an improvement over the download from www,siteadvisor.com.. When I tried to install it on another PC, I got a message that this PC had a later version [I don't know where I got it] anyway I looked under options/ settings/about. and it shows V220.127.116.11...which indeed does appear newer..but there IS the "not signed" warning under add-ons. The version numbers shown under add-ons differ from the ones shown under options/ settings/about...the PC with V18.104.22.168. under add-ons shows webadvisor 4.06 "last updated 9/7/15.
On 2 PC's when I try to install the same V 22.214.171.124 and my browser is the same Firefox V42 [the latest V], I get error message "Your installation cannot continue because your browser does not meet our minimum system requirements. Please update your browser and try again. There are many other inconsistencies, but this a post not a Wikipedia article.
Every other Add-on, I have 23...including several security add-ons like WOT, NoScript, Disconnect, Ghostery, is signed and updates when when I hit "check for updates" under add-ons. WebAdvisor is a mess...I'm trying hard to get up to date signed versions on each of 6 PC's and can't seem to pull it off.