Why did my kitten poop outside the litter box?

A cat is delicate and subtle in nature. Unlike
dogs they cannot show their unhappiness by tearing sofa or bed covers. They
have different ways of expressing themselves.

http://catfanlover.com/cat-peeing-everywhere-here-the-solution

It's still a kitten and learning. Also. Kittens are like children. They need to be trained and they will have accidents.