Temporary health buffs also serve as a healing. Following this I would say it becomes a 7/8.
Here you can find someone complaining about this and also a good explanation by user OracleWawa.
He had a similar problem as you do. He had two damaged murlocs which got buffed by a warleader but upon removal of the warleader the murlocs did not drop back down in health.
This explains the interaction:
If an aura buff provider like Stormwind Champion or Murloc Warleader
is on board and buffs a minion who wasn't at his full health (or you
hit that minion down to like 2 HP and then remove Stormwind Champion
from the board) the HP will stay the same. It's a thing you need to
Basically minion's HP will increase when it's max HP increases too
with any kind of way (Power Word: Shield, Stormwind Champion etc.),
but if minion's max HP would be decreased but not below his current
HP, his current HP won't change. And technically any HP buff,
including aura minion buffs like Stormwind Champion are max HP buffs.