Updating Mac app shared with Family Sharing prompts for family member's password
I'm trying to update a paid app, bought by a family member but shared with family sharing, on the Mac App Store, and it prompts me for a password. The Apple ID in the dialog is the family member's, and greyed out so I can't change it. I don't think we're supposed to share all of our passwords in order to use Family Sharing, right?
macOS High Sierra (10.13.1)