Turns out Firefox has a similar issue, despite mitigations :( https://bugzilla.mozilla.org/show_bug.cgi?id=1372288

This only happens if the extension puts their `moz-extension://` links into the DOM. It's different to chrome case where extensions can be detected regardless of being activated on that site or not.

	▲	lxgr an hour ago \| parent [-]
		As I understand it, an extension could also leak its links via its own backend, e.g. to advertisers, who could then detect it even though no user-observable DOM modification is happening. Much better than static global IDs, but still not ideal.