'Import Office File' button doesn't work on IE11 and Edge

STEPS TO REPRODUCE

Preconditions: The XWiki instance must have Office Server configured and started.

1. Start XWiki in IE11/ Edge browser
2. Edit a page with CKEditor
3. Click on 'Import Office File' button
4. Click 'Browse' and select an Office document
5. Click 'Import'

EXPECTED RESULTS

The Office document is imported into the page.

ACTUAL RESULTS

The 'Import Office File' button doesn't do anything when clicked, so the Office document cannot be imported into the page.
The issue can be reproduced on IE11 and Edge browsers, on Chrome and Firefox the button works.

The issue was initially reproduced by @Alexandra Ifrim.