Can't attach images with pipe (|) in the name via drag-and-drop or image dialog

Files which have a pipe in their filename cannot be uploaded into Confluence. When trying to do this via dragn-and-drop, it appears as an image icon in the editor. When using the insert image dialog, it tries to make your browser download 'attachfile.action'.

Workaround: rename the file so it doesn't contain a pipe, then try uploading the file again.