A flash and smoke grenade exploit has been discovered on the CS: GO beta by a chap called “Deman”. He highlighted the exploit on the Steam forums and provided instructions on how to do it.
Type sv_cheats 1
Exec the configs or enter them manually.
Type sv_cheats 0
Join a server, if it doesn't works disconnect and repeat the steps listed above.
VAC proof since it doesn't alter any files and is purely a cvar exploit.
Following the above instructions will make you immune to flash grenades and will allow you to see through smokes much more clearly. Bear in mind that this exploit may work fine now but will most likely be purged in the next update on Friday.