It's not hacked, as far as I can see. I enabled bitcoin paying ad network a-ads a couple of weeks ago and it may be that some people saw some ads on that network, which looked fishy and reported them. I'm filtering all NSFW, Shady and Gambling ads from a-ads, but if the IP belongs to that network, then it will just fall under the filter. At least that's my opinion now... Will look into it further...
It may also be some dirty competition move, but who knows :)
This was my first assumption(dirty competition). But keep in mind your site is not accessible unless you disable the extension. Traffic is redirected to https://metamask.io/phishing.html.
It seems the blacklist is updated via github https://github.com/409H/EtherAddressLookup. Though I couldn't see your url there when I took a quick look. Hopefully if you investigate more you'll be able to find the root cause.
Thanks a lot, appreciated :)