Unable to attach file to a Confluence page in edit mode

Summary

When a page is in edit mode and you drag a file from your computer and drop it directly into the page's body, the file is never uploaded and the upload modal says it's uploading the same files 2 times, however the upload status is just "Waiting".

Environment

Confluence Cloud version 1000.139.2

Steps to Reproduce

1. Go to a Confluence page and edit it
2. Open your computer's file explorer (Finder, Windows Explorer, Nautilus, etc)
3. Drag one file from it and drop it within Confluence's page editor

Expected Results

The file is uploaded to the page

Actual Results

This one file appears twice in the "Attach files" modal and the status "Waiting" never changes and the file is never uploaded.

The following appears in the browser's console:

Workaround

Attach the file from outside the editor click the Options button (3 dots) > Attachments.