Apple has identified a vulnerability within OS X High Sierra that allows unauthorized users access to a computer without inputting a password. This issue was already mitigated on all ITS managed Mac devices.
What do you need to do?
Verify that you are using OS X High Sierra: Click the Apple menu, select About This Mac, and confirm that it lists High Sierra. If it does not, you do not need to take any further action; all other versions of OS X are not affected.