Player is able to see and in some case fire through the walls. As i tested it depends on the thickness of the wall. If the wall is too thick the the player is unable to fire through it.
When i mention fire through it, i mean it is able to fire without wall penetration. Basically the bullet appear in or behind the wall and that is why the player is able to shoot through it.
There is two way to do this hack/cheat. See the steps to reproduce section.
Demo:
https://www.youtube.com/watch?v=07oOWE1UXIg
A. with rifle or pistol
You will see through the wall and some cases you are able to shoot or throw grenade to the other side of the wall. It is really funny if you are in the building and shooting out.
B. without weapon
Gamermanas made a simple script which black out the view if the player try to use this glich exploit.
http://forums.bistudio.com/showthread.php?183764-Glitch-Exploit-Cheating-and-new-DLC
I think this similar fix is a welcome solution in the vanilla game too.
Are you planning to fix this? This is a public issue and i have seen that many times in the KotH servers.
Have you seen the Glitch fix video? http://youtu.be/kynv_woKPTo?t=1m54s
I think as a first iteration(hotfix) it would be enough.