Hey there everyone, the more i play this game, the more i find tiny glitches and bugs to share with y'all... They might not be that high tech or crazy but they work for me!
So my friend and i were playing Extinction for the first time and we got the Challenge: Kill 25 or so enemies while in prone.
We were just chilling in prone with our shotguns out but it was getting annoying and i almost just wanted to get past that hive, so i activated a trap. Once the trap was activated, i went back in prone so i didn't look like a douche to my friend, and while being in prone, not shooting at all(either of us), the aliens begin to run into my trap and it counted towards our challenge.
tl;dr
Activate traps, as long as you are in crouch/prone it count's towards their challenges.