Do not know where to post this; more of an information thing than a question.
For the past few days, when I hit the Bookmark for CCleaner Discussion Piriform Community Forums I get a page telling me that Firefox has prevented this site as it may be misconfigured or my clock may be set wrong. Well, I doubted that either of these things were true.
What I finally did was simply to delete the bookmark and then bookmark it anew for the Forums. No problem whatsoever. This was the only site that gave me the message. Do not know what happened but if any one else has this problem, try to delete the bookmark and then bookmark it again.....
The old forum web address (forum.piriform.com) was changed some time ago (to community.ccleaner.com), and so any old bookmarks/favourites that were pointing to the old address were being redirected to the new one.
I've just done a quick test and if you try to use the old address then Firefox will now throw a block as you describe rather than redirecting.
(So will Edge Chromium, and other browsers).
I suspect that the SSL for the old address may have expired. I'll point it out to the staff.
EDIT I've just checked and the SSL for the old address did indeed expire on 12th October, it just needs to be renewed.
As you have found creating a new bookmark (or editing your existing bookmark) with the new forum address is the thing to do if you are having problems with the redirect.