I agree with the feedback quoted below. If I'm navigating, I'm expecting that my history 'pops' back to where it was when I entered the viewer, as this is an application inside the current discreet page. Now each separate view is acting as a discreet page, which is just a little bit too much.
I classify this as a bug, because it is messing with my expectations of using a website.
To quote from the feedback page:
Media Viewer functions as a discreet page making navigation awkward[edit source]
First, I'll be blunt: I don't care for this new media viewer and I don't see what purpose it serves on an encyclopedia. I use Wikipedia for a fair amount of image research for personal projects, as it's a great way to find things in the commons. As such I often click on images, read their description pages, and figure out if I can use them or not before continuing my research. Not only is the information that was readily available just last week now buried in the fine print, but the "application" apparently functions as a separate page, even though it in no means looks like one. If you close the "application", as you would visually similar applications on popular social and photo-sharing websites, and later hit the back button the navigate to your original search, you find that it takes you to the media viewer. If you've viewed and closed multiple images on a page this can lead to an unnecessarily large amount of clicking to navigate back to a page you thought was immediately previous to the one present.