I wouldn't personally use a proprietary extension with access to every tab, but: Extensions written for Chrome can be hand-ported to Firefox in the span of ten

I wouldn't personally use a proprietary extension with access to every tab, but: Extensions written for Chrome can be hand-ported to Firefox in the span of ten minutes, even if you don't have unminified source code. There used to be an extension that automatically did it, but I can't remember what it's called. WebExtensions are pretty neat!