How to attack through vulnerability PC in Internal network to another device in it.

I got ask this qeustion in interview that I can't answer it idk how to call this trick as well, and PC in Internal Network it doesn't have any tool about penetration only thing you have is controll that PC.

-From my [Diagram](https://imgur.com/a/NZ52TMz)

ask attack call can cybersecurity device internal internal network interview network penetration tool trick vulnerability