There is a new setting in Hub that restricts the visibility of items belonging to a Collaborative Space (for example Tasks in the Task widget). One option is to make sure The Space is marked as Private. This will automatically make items visible only to the space they belong in.

However, if an admin wants this done on public spaces as well it can be achieved by updating the application settings. Navigate to "Admin and Settings > Applications > Application Settings > Foundation Hub" and the setting will be under the General section at the top. Click edit and look for the "Search across all Collaborative Spaces:" option and set it to "No". Once changed users will only see items belonging to the Space they are currently logged into.

The only exception to this is if a user belongs to the Service Account Group.