How do I get the current url inside a firebug extension?

How do I get the current url inside a firebug 开发者_运维问答extension when for example pressing a button?

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Does that mean you create an extension for Firebug? I am not sure about that, but in extensions for Firefox you can get it with

window.content.document.location

Sorry if I misunderstood the question, it is not totally clear to me.

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Just hover the element and right click to select "Inspect Element" to view details.