In the Service Portal, drag-and-drop attachments are not working on a record producer or Service Catalog item. Instead, the attachment is rendered/opened in the window, which redirects away from the ServiceNow page.
Steps to Reproduce
Go to Service Portal > Service Portal Home.
Click Order Something, and select the Apple Watch.
Drag and drop a a file to attach it.
Note that the attachment is opened in a window that redirects away from the ServiceNow page rather than the file being attached.
Use the Add attachment function to add attachments by clicking the paper clip icon at the bottom of the page.
Related Problem: PRB714638