Thank you for the clear explanation. This is good enough for me I guess then. What I am most afraid is not really a colleague building a malicious package on purpose, but rather them installing something which is then run as root and gets access to the whole system. I understand packages are built by unprivileged users, but in the end they are owned by root.

What I wonder is whether in the way it is possible that something is run as root without someone specifically deciding it should be.