Dragging an existing image and dropping it elsewhere on the page in IE11 results in a duplicate attachment

Summary

Dragging an existing image and dropping it elsewhere on the page in IE11 results in a duplicate attachment

Environment

• Tested on Confluence 5.8.13, 5.8.18, and 5.9.10
• Can reproduce using IE 11
• Can NOT repro with Chrome, Safari, or Firefox

Steps to Reproduce

1. Create a page with an image on it
2. Using IE11, click and drag the image, then release the click elsewhere on the page

Expected Results

1. Nothing

Actual Results

1. Image is duplicated, with a [1] added to the filename
2. Subsequent attempts to drag and drop show the same behavior in the UI, but no additional images are created beyond the first copy (i.e. you end up with 2 duplicate images attached to the page)
3. Thus, all users watching the page are notified of the new duplicate attachment, resulting in needless email

Workaround

Use Chrome, Safari, or Firefox instead