User scripts can use this object to access "custom" properties--variable and functions defined in the page--set by the web page. This is done by bypassing Greasemonkey's XPCNativeWrapper-based security model. unsafeWindow is shorthand for window.wrappedJSObject; it is the raw window object inside the XPCNativeWrapper provided by the Greasemonkey sandbox.
unsafeWindow is insecure, and should be avoided when possible. User scripts absolutely should not use unsafeWindow if they are executed for arbitrary web pages, such as those with
Alternatives to unsafeWindow
If a user script must execute a page function, it can use the location hack to call it safely. This involves setting location.href to a
Larger blocks of code can also be executed this way:
This code will run in the page context without leaking the sandbox. This code is completely separate from the rest of the script scope, sometimes limiting its usefulness. For example, data cannot be returned by the function.
Another drawback is that this technique is rather ugly. Still, it is preferred over unsafeWindow.