The Photos module in Oasis has a button that let users upload new files in a pop-up window, but it lacks the functionality of Special:Upload to add instructions or warnings to users that want to upload files, so people often use that to upload random images that would never be used on articles.
It also hides the options to add a description, select the proper license and put a correct filename, giving no warning if the image already exists or if it was deleted before. This leads to a mainteinance overhead to the local admins.
How to disable it Edit
Note: Code updated to work with the new async load of the sidebar.