Wow, 18 years to grab the current URL from the active tab? I am trying to dump Chrome forever but some automation/scripting that I rely on requires being able to programmatically obtain the current tab's URL from AppleScript or via some other CLI interface. Is there any way this can get some attention? Seems like the plumbing is already in place, since the following returns quite a lot of info about the current tab, just not the URI/URL.

tell application "Firefox"
	get properties of front window
end tell

For what it's worth, some hacky workarounds for this are discussed in this thread on the Keyboard Maestro forum. Although the details of that discussion are fairly specific to Keyboard Maestro, many of the same techniques could be achieved using 'plain' AppleScript, though with a little more effort required.

A contributor is working on this in bug 1655268.

A slightly simpler workaround than the ones linked to in Keyboard Maestro land is to use something like (or exactly) this extension:
https://github.com/erichgoldman/add-url-to-window-title / https://addons.mozilla.org/en-US/firefox/addon/add-url-to-window-title/

set extension preferences to show full url & then use a script like

on explode(delimiter, input)
	local delimiter, input, ASTID
	set ASTID to AppleScript's text item delimiters
	try
		set AppleScript's text item delimiters to delimiter
		set input to text items of input
		set AppleScript's text item delimiters to ASTID
		return input --> list
	on error eMsg number eNum
		set AppleScript's text item delimiters to ASTID
		error "Can't explode: " & eMsg number eNum
	end try
end explode

tell application id "org.mozilla.firefoxdeveloperedition"
	set wintitle to name of (get front window)
	
	return last item of my explode("- ", wintitle)
end tell