as said by "Firefox user 14598161" (19 days ago), addon description is a big LIE!!!
=> there is NO "UNLIMITED and 100% Free VPN server", after use of 1000-1500 MB(! = daily traffic limit) the account will be locked on 24h!
this is a bit conidence tricks! NoGo.
and all the uncritical cheer-reviews seems to be self-made by SetupVPN!