The Kaldorei Conjurers in the drowned market (Nazjatar) have a 50% increased haste for 5m buff that will auto refresh itself on anyone who spellsteals it when it gets to the last minute of the buff. Sometimes, you will even double up in the last minute!
If your character is unable to cast (silenced, mounted) it will eat the refresh and you will have to get it again.
This will probably get fixed in the first round of hotfixes so enjoy it while it lasts!
---confirmed fixed!