Drag and Drop doesn't work when uploading files from Page Attachments

Summary

When accessing Page Attachments *** > Attachments, the Drag and Drop box provided is not working. Dragging a file to this box no longer starts the upload but instead it's opening the file.

Environment

Confluence 1000.916.3
Mozilla Firefox 51.0.1
Google Chrome Version 56.0.2924.87 (64-bit)

Steps to Reproduce

1. Access Page Attachments *** > Attachments
2. Drag and drop a file to the Drag and Drop box

Expected Results

• Dragging a file to the Drag and Drop box should upload the file.

Actual Results

• Dragging a file to this box no longer starts the upload but instead it's opening the file.

Workaround

• Use the Upload file > Choose File