I have tried to add the image on product description, but its placed on the short description field ( Magento 2.7)
Steps to reproduce
1.Go to catalog product and Click "Add Product"
2.Go to "Content" area
3.If already open, close WYSIWYG editor for every field.
4.Re-Open WYSIWYG editor for the Description field
5.Click on Insert Link, choose any image and click "Insert Image"