Replication steps:-

1. goto a course settings and select "hide sections completely that are invisible" for "Hidden sections" setting.
2. Hide a section
3. As a student try to access this section page (course/view.php?id=37&section=12).

Since a blank page is shown instead of error, student can know that the section exists but is not visible.
IMO this is a minor security risk, as it gives away the information if the section exists or not.