Protocol 26: everyone in a session needs this version.
A door, safe or lock change from a friend counts only when they stand near it; a world state on joining is taken as it is.
An NPC a friend kills falls where it fell in their game, so the corpse and its loot are in the same place for everyone (deaths replayed to a later joiner still land where that game had the NPC).
Everything from 0.7.5 to 0.7.7 (stability audit, trust limits on the host and in each game).