CF can be a bit of a pain to set up on a dynamic site (not static content, but a forum where the content changes constantly), but it's otherwise pretty tame.
This is almost certainly one of those two things - automated defenses or a change made at the top.
I could give you more information, but I'm not privy to the server logs. I can't check the traffic to see what percentage of it is malicious. (There's always a sizable percentage of traffic that is malicious on any site that's indexed by search engines.)
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But, the key takeaway is not to worry, not to fret. It's nothing more than a CF (a CDN) interruption. Just authenticate and tolerate it until it goes away. It's nothing to be alarmed about and the admin will know about this when they see their messages.