Ask HN: Anyone else seeing this weirdness in the Opera web browser?

Yesterday while using the Opera web browser on my late `09 Mac Mini (MacOS v10.11) to test a web app I'm working on I noticed a <style type="text/css"> tag referencing a file that's not in my html code. Here's a small sample of it of what was in it: :root topadblock, :root span[id^="ezoic-pub-ad-placeholder-"], :root img[alt^="Fuckbook"], :root iframe[src="mellowads.com"], There are hundreds of URLs embedded in that file and not all are porn sites (but there are quite a few). My first thought was I may have some malware on my Mac but after testing the app on Firefox and Safari and not seeing this issue I thought maybe this is a "feature" in the Opera web browser so I sent them a message via the bug report system on Opera's web site. They replied with: "All bug reports are read and handled by our staff. However, please note that you will not receive a personal reply to the bug report, unless we need more information to investigate the bug." Later on last night I did some searching for a file with that string above in it on my Mac and found one buried in one of the system folders named "OperaEmbeddedBS.html". So this morning I responded to Opera's reply email asking if that file is installed when I install their browser. So far I've not heard back from them but it's only been a few hours. I've also done some google and duckduckgo searching for both the file name and snippets of the content but didn't find anything at all. I've uploaded the file so others can check it out if they want: https://ezinvoice.com/OperaEmbeddedBS.html The page is blank when viewed in a web browser so you have to view the source code to see what it contains. Here's another longer snippet of it copied from a page loaded in the Opera web browser. I have no idea what this does. I've never seen CSS like it before but that doesn't mean much because my CSS skills and knowledge are minimal. Anyone have a clue about what this does, if it's an Opera "feature", or malware of some kind? The only thing I can think of is it's sending requests to the urls embedded in it, but I no clue why or what else it might do. <style type="text/css">:root topadblock, :root span[id^="ezoic-pub-ad-placeholder-"], :root img[alt^="Fuckbook"], :root iframe[src="mellowads.com"], :root div[style^="padding: 5px 15px !important"] > [style^="width: 100% !important; cursor: pointer !important;"], :root div[id^="zergnet-widget"], :root div[id^="traffective-ad-"], :root div[id^="taboola-stream-"], :root div[id^="sticky_ad_"], :root div[id^="rc-widget-"], :root div[id^="q1-adset-"], :root div[id^="proadszone-"], :root div[id^="lazyad-"], :root div[id^="gtm-ad-"], :root div[id^="ezoic-pub-ad-"]