Note: A small number of add-ons may be listed as unsupported or may not appear in about:addons. Their data is not lost; users should be able to re-install the add-ons and recover the data (Bug 1549129). More support information
Available via the internal updater: Help / About Firefox
Windows 7 Pro SP1 (64-bit), avast! v17 Free, MBAM3 Pro, Windows Firewall, OpenDNS Family Shield, SpywareBlaster, MVPS HOSTS file, MBAE Premium, MCShield, WinPatrol PLUS, SAS (on-demand scanner), Zemana AntiLogger Free, IE11 & Firefox (both using WOT [IE set to WARN, FF set to BLOCK]), uBlock Origin, CryptoPrevent.
[I believe computer-users who sandbox (Sandboxie) are acting prudently.]