Players are able to locate other players permission with lightning/thunder sound locations

Players can locate other players locations when lightning strikes. We had to turn of weather on our server (snapshot.pandamium.eu) due to this problem.

 

from my knowledge, they either use a hacked client which exploits this bug, or have another alt nearby. What these alts do is use two different directional sounds to pinpoint the location of a player. This has been a big issue as hackers have been able to find (and grief) bases, thousands, if not millions of blocks away.