Yes foxes can climb very easy and have strong claws that give the fox the ability to climb things such as trees with ease.
I've seen foxes climb trees and I saw a fox climb up some scrap cars at a scrap metal yard and just sit there like it was watching the people in the scrap yard.
The fox was not harming anyone but just seemed to enjoy sitting there.
Foxes will sometimes climb things such as trees and other things to get to prey or to get away from danger.
Most foxes are harmless to humans as long as you treat them good and don't go near them unless they want to approach you.
About 5 years ago now I was out camping in a tent and a fox came up to me and the fox was very friendly and must have been around people before.
The fox let me pet it and I gave it some food and then it went on it's way.
I wish I could have gotten a picture of it or video of it allowing me to pet it and feed it but that probably would have spooked the fox away anyhow.