UnsafeWindow
From GreaseSpot Wiki
This command can open certain security holes in your user script, and it is recommended to use this command sparingly.
Please be sure to read the entire article and understand it before using it in a script.
Syntax
unsafeWindow
Description
Userscripts can use this object to access document functions, variables and other elements in the document. unsafeWindow is a object wrapper for the entire document object.
Examples
unsafeWindow.document.title="Testing" unsafeWindow.TestVarCreatedByDocument="Testing" unsafeWindow.document.TestFunction("Test")