is safari extension global page JS able to modify a tab's DOM?

Question

This page describes the Windows and Tabs api for Safari extensions:

The Windows and Tabs API

My question is: Does Javascript loaded in the global page have the ability to manipulate a tab's DOM?

Or, do I have to inject JS into a page as a Start / End Script in order to get access to a tab's DOM?

Answer 1

Do I have to inject JS into a page as a Start / End Script in order to get access to a tab's DOM?

Yes.