I had an exam (as an assignment with a Word document attached that contained the questions because it was essay format and that's how I wanted it) that was unpublished for a few days on Canvas before I wanted my students to have access to it. I set the access dates so that students would not be able to access it until the beginning of the exam time. However, some student's access reports show that they viewed the files before the access was open. Does the "Files" tab publish the files you upload even if the assignment is unpublished?? Could the students go search the Files tab and view the materials prior to when they are supposed to have access??