I am curious that both websites have 'finity' as a suffix.
It is possible that furaffinity itself has hosted a compromised advert, so I will
@Dragoneer so that he is aware of this thread.
But the 'finity' suffix makes me suspect that the 'xfinity' redirect page is a malicious scam that is impersonating ComCast's legitimate xfinity business.
I think the malware is detecting when a user attempts to visit a URL that looks similar to 'xfinity', and then redirecting them to a compromised page in order to trick customers into giving their financial details to criminals.
A user who intended to visit xfinity because they are an actual customer could be tricked into believing they were given a special offer.
I note that the URL in the screenshot is clearly
not the url of ComCast's legitimate business.
The fact that Smity said deleting the cookie cache temporarily removed the problem suggests the piece of software performing the redirection was delivered as a 'drive by download' that is exploiting your browser or plugins.
en.wikipedia.org
These are usually delivered by third party adverts which have not been scanned for malware before being hosted.