Mozilla built in Firefox to show advertisements for the paid Mozilla VPN service, implemented in the form of a pop-up window that overlaps the contents of arbitrary open tabs until the ad block closes, blocking work with the current page. In addition, a bug was identified in the implementation of displaying ads, due to which the ad unit popped up during operation, and not after 20 minutes of user inactivity, as was originally intended. After a wave of user dissatisfaction, showing Mozilla VPN ads in the browser was disabled (browser.vpn_promo.enabled=false in about:config).
In the submitted complaints, users emphasized the inadmissibility of the intrusive method implemented by Mozilla to promote their services, which interferes with the work in the browser. It is noteworthy that the close button was almost imperceptible in the advertising window (a cross merging with the background, which does not immediately catch the eye) and there was no opportunity to refuse further display of advertising (to close the blocking advertising window, the link "Not Now" was offered, without the possibility final rejection).
Some users have reported a browser freeze during the display of an ad unit, which lasted about 30 seconds. Site owners also expressed their outrage, as inexperienced users had the impression that this site displays intrusive advertising, and not the browser substitutes it.
Source: opennet.ru