In Svetloyarsk I and one more survivor I just met were attacked by the invisible player.
Nearby there was a person though he seemed to be dead or lagged. Every time when I approached him close, someone invisible started to hit me.
The similar happened several times to my group on this server, but to me for the first time.
I believe it's some new kind of hacks. Because no zombies were close to our place.
Noone could ever make those hits.

https://youtu.be/nnf6v2MysTY