Guild Wars 2

How do I get “Halloween events completed” Achievement ?

I thought I can get it when I finished the scavenger hunt. But it doesn’t or is it a bug ?

its in ur achievement tab

Achievements
Scroll down to:
“Special Event”
Complete everything below

WARNING:
Title track is bugged to hell and does not update correctly upon completion of subachievements. Multiple threads have been made about this so it will be fixed whenever ANET feels like it.

Proof of Bug
http://i.imgur.com/M9xda.jpg
1+1 = 2
1 point in main track
wtf?