From inside the vi editor a pen tester executes the following command:

:$!/$bin$/$sh

What are they doing?

From inside the vi editor a pen tester executes the following command:

:$!/$bin$/$sh

What are they doing?

saving the contents of the editor as an executable binary named sh

attempting to start a terminal shell

replacing all occurrences of the text "bin" with $"$sh$"$

saving the contents of the editor to a file named sh in the bin directory