Cube edges squished?
If you look closely to your print you will see that the edges are part of the problem, e.g. you also have a problem called "Elephant foot" where the base shows a fairing to the build plate.

The elephant foot deficiency is caused by an imbalanced choice of bed and hotend temperature and print cooling. This imbalance also causes the edges to collapse (probably also caused by the infill, or lack of it).

You should look into finding a better printing temperature combo and experiment with little cooling. This will also help you to better print the rest of the cube.