(I haven’t heard anything about this, and from what I do know of Firefox I can’t see how anything even vaguely like what I think you’re describing would be technically feasible.)
https://old.reddit.com/r/firefox/comments/uovcdh/only_a_rumo...: multiple authenticated sources confirm this to be a fake. Beyond that, some details about the presentation of the page don’t match what you’d expect (covered in the comments), and the terminology in the comment looks quite wrong to me too (it’s a mixture of technically incorrect, suggesting technical unfamiliarity, and overly specific, suggesting technical familiarity).
(I haven’t heard anything about this, and from what I do know of Firefox I can’t see how anything even vaguely like what I think you’re describing would be technically feasible.)