Categories blocked, but not their posts

Brand new to this plugin and I’ve set up a public and a member post category and posted within both. Set up level public and member as well, and set ‘stranger level’ to public. That all works so that I only get public list of posts if I am a stranger, and if I am logged in as a member I get both public and member posts listed.

My issue is the following. When I am in stranger mode and if I for some reason know the URL to a post within the member category, I can still access those posts without any problems.