New bug discovered in MacOS High Sierra allows unlocking App Store System Preferences by any password. This bug allows anyone to login to the local admin account with the username root and no password needed. This could be very dangerous if anyone already has your system permission and they can able to download any apps, modifying the apps store setting, also they can disable auto update for future MacOS update. Apple released a statement saying, We greatly regret this error and we apologize to all Mac users.”]
Source: https://gbhackers.com/macos-high-sierras-app-store-system/