Access to Discussion without Having to Log In

Anyone with the link to a subgroup can access and navigate through the pages of that subgroup without having to log-in to Groupsite. We have sensitive information/alerts/discussions posted and public access could be very detrimental--in some cases a serious security threat, especially as we approach the upcoming elections. Is this a flaw since the update, and are there immediate plans to keep unsubscribed users from accessing the site? My members need the assurance that they can have safe and protected discussions that only approved subscribers are privy to. The naming of the links is not hard to guess, so if someone were to discover this flaw, they could systematically access the entire site.

Or maybe there is something I need to do as admin to prevent this?