I do not wish to see advertisements for Mullvad on my Private Browsing new tab pages. But I can't even seem to opt out of them, as they remain even after searching "Sponsored" in about:preferences and unchecking all the applicable boxes. uBlock Origin also seemed unable to remove them, even with a custom filter and after enabling it on about-scheme. So I went to fix it with userchrome CSS, by adding the following to a file named userChrome.css inside a folder named chrome inside my profile folder (after setting toolkit.legacyUserProfileCustomizations.stylesheets to True): [code] /* Remove advertisements for Mozilla VPN */ @-moz-document url(about:privatebrowsing) { .promo { display: none !important; } } [/code] However, even after restarting the browser, these advertisements are still present. What am I doing wrong?