What version are you running?
2.0.x
What's the URL of the page containing the problem?
http://<server>/r/<id>/
What steps will reproduce the problem?
1. Log out.
2. Drag-and-drop a file onto the review request
What is the expected output? What do you see instead?
There shouldn't even be a drop indicator of any sort. Instead, we're getting a drop indicator, followed by a thumbnail placeholder with a spinner that spins forever (since the file can't actually be uploaded).
Please provide any additional information below.
Note that this likely happens for review requests not opened by the user as well. This should be checked. (Make sure you're using a user not configured as an admin.)