Tested Browser: IE11

Set up Anonymous permission
On the Global Permission set confluence-users --> Can use

Give an Anonymous permission to a Specific Space under Manage Permission:
1. Add pages
2. Add / Delete Attachments

Scenario:
1. Create a new page
2. Add word / excel file and save (--> Will save as expected)
3. Create an additional page and drag a file

Actual: You'll end with a permission error: "You are not permitted to attach files on this piece of content. You may want to contact null for permissions to do this."

Expected: file should be added successfully

Note that this only happens on the second page create.