Apple suggests the workaround also discussed in this thread until the issue is fixed: "We are working on a software update to address this issue. In the meanti

Apple suggests the workaround also discussed in this thread until the issue is fixed: "We are working on a software update to address this issue. In the meantime, setting a root password prevents unauthorized access to your Mac. To enable the Root User and set a password, please follow the instructions here: https://support.apple.com/en-us/HT204012 https://support.apple.com/en-us/HT204012. If a Root User is already enabled, to ensure a blank password is not set, please follow the instructions from the ‘Change the root password’ section." https://techcrunch.com/2017/11/28/astonishing-os-x-bug-lets-anyone-log-into-a-high-sierra-machine/ https://techcrunch.com/2017/11/28/astonishing-os-x-bug-lets-...