Drag and drop picture into the editor doesn't put it at the cursor position when using Firefox

Summary

Drag and drop picture into the editor doesn't put it at the cursor position when using Firefox browser

Environment

• Confluence 5.10.x , Confluence 6.x
• Firefox 52 and 53
• Firefox Quantum 61.0.1

Steps to Reproduce

1. Create a page and add some content
2. Position the courser somewhere in your content
3. Drag and drop an image

Expected Results

The image should be add where the cursor is positioned

Actual Results

The image is added randomly in the content

Notes

The problem is not reproducible with Chrome or IE