Hi @jamiemccardle,
My apologies but I'm struggling to understand your question. When you say the category is hidden, do you mean it has the setting "hide from lists and menus"? That is definitely different from having a user or group of users from not being able to access the category (and/or boards within) which must be done via permissions. Unless the users do not have access to view that category via permissions, it would be expected that they could see content.
Could you perhaps give us some more context about what you are hoping to achieve so we can assist?
Jason
Thank you for your reply. I want a category to be open so anyone can access, but hidden so they can only access if I share the direct link. if a create a post in that category, it'll still appear in the Community Activity until enough posts are created to push it off the list.
Thanks for clarifying @jamiemccardle
Only way I can imagine you will get what you want is to replace the (what I assume is) your home page and category page post activity feeds from the out-of-the-box components to an API feed in which you can write the rules. Eg only take posts from x and x but not y.
Jason
