Docker

Switching to the root USER opens up certain security risks if an attacker gets access to the container. In order to mitigate this, switch back to a non privileged user after running the commands you need as root.

Using the FROM instruction is a huge exercise in trust, you have to trust that a particular version or an image is safe for you to use, and that it will never be retagged maliciously. In order to prevent that, some companies copy trusted images into their own repositories, and reference them directly.