Problem with the progression

[GrabiouL]

Hello !
I have notice a bug that allow me to get things that i'm normaly not able to get.
For exemple, when I start at lvl 1, if I pick up like a Type-2 (only enable at lvl 22), I can earn XP for it and obtain attachement or even Camo.
An other example, to get to the Headshot challenge, you need first of all to get kills, but for some reasons, I'm able to get those challenge if without finishing the kills challenge.
I don't know if it's only me, or what causes this, but when I've first played IW7X, like 5 months ago from now, this bug didn't exist, I've played till Prestige 1 and i didn't notice anything about this.
Thank you for taking the time to read me, and wish you the best for the future !