To reproduce: I added a password protected page to our site, some sample text, and set a featured image.
Then I selected this protected page as a featured page on the customizr config page. It then shows the proper featured image for the protected page as well as prepending "Protected:", but it also had the first (supposedly secret) sentence or so from the protected page there under the nice circle graphic :) I would attach an image to this report but I can't see how to.
Not sure if this is a WP problem or the theme code needs to check page properties before rendering the featured item area...
Simple workaround is to explicitly set the featured text for that item and it replaces the snippet taken from the protected page.