>>ReadCa+(OP)
Last year Firefox displayed a Disney ad (for the movie 'Turning Red') on the whats-new tab, the tab gets diplayed by default after you upgrade to a new Firefox version I think. US users only.
>>rrdhar+kj
Not to defend Firefox, but I believe Mr Robot is what caused them to make a visible toggle for experiments. Sadly it's not off by default, but once it's turned off, you don't really have to worry about it. That said, I never saw this VPN popup.