mrkgnao: I get the same issue (barring the ominous black and red sphere in the background) in the last couple of days and I don't ever log out or use a secure connection (except where mandatory). I get it simply by visiting the home page. I have seen reports by others to that effect.
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The sphere is from the theme I'm using on Firefox, and have been using for a very long time now, so I doubt it has anything to do with this issue.
I just filed a support ticket, will update when I receive a reply.
mrkgnao: [...]
I tend to believe that GOG is trying to redirect me to Steam, but Valve is refusing to accept the redirection.
And here I was thinking that GOG wanted to achieve the exact opposite, silly me.
(Cheers for the chuckles)