But private forum items show in the widget to everyone and private topics don't.

wpForo Doesn't show private forum items to everyone. Are you sure your forum is private? And are you sure you check it after deleting cache and with correct user/usergroup?

Here is an example. wpForo has Private Category and Private Forum:

Both are set with this permissions (not only the parent, both! All should have correct permissions):

It shows for admin, but not for you. Can you see this?

Also check the "No Access" forum access and make sure it looks like this:

Okay, not totally private. I have a forum for mods and it is restricted to mods but all can see topics and replies in the widget. Look at my first post, you agreed with me...

I've already explained. You just need to correct your permissions as it shown above. And please don't say that forum is Private. If Forum Permission is not totally disabled it can't be called as private. So saying wpForo shows topics of private forum is also not correct.

Okay, I've tested it (without changing anything) and it works. Something must have been fixed since I logged this originally. Happy to close this thread off now.