In this level we need to get a shell, as before we only had a text editor.
In vim there is a command :shell, which opens a shell. The problem is that when we run this it looks in /etc/passwd and just runs more again. We can, however, set environment variables in vim.
:set shell=/bin/bash
This means that when we run :shell it will run bash, giving us what we want.
Looking in the home directory we have a suid binary, similar to level 19.
./bandit27-do cat /etc/bandit_pass/bandit27
This reveals the password: YnQpBuifNMas1hcUFk70ZmqkhUU2EuaS