After upgrading our Jenkins instance to 2.7.1, we have noticed that the configuration area of existing jobs do not display correctly (as seen on the screenshot).

A bit of experimenting has shown that entering long user/group names in 'Enable project-based security' block (in an old, freestyle job) increases its width, and eventually exceeds the block it should fit in. At that point, all boxes become too large, and the resulting UI is very hard to read.