I don't know if I would necessarily classify this as a bug, but it did produce some unexpected behavior. It took a couple of minutes for me to figure out what was happening.
When editing an the files associated with an item, you can click and drag the files to change their order. A couple of times when I have done this, I've clicked and dragged on the file name, which changes the order as expected. But, because I clicked the file name (and it's associated anchor element), it also opened up another window/tab in my browser to view the click item.
-Matt