https://www.theverge.com/2018/1/11/16877992/high-sierra-bug-apple-app-store-settings-password-preferences

A new bug has been discovered on devices running macOS High Sierra that allows anyone to access your App Store system preferences. The bug was spotted by MacWorld, which also notes that it’s most likely the bug will be fixed in the next update as users running the 10.13.3 beta haven’t been able to reproduce it.

To check if you’re affected by this bug, open system preferences on your Mac, click on App Store, then if the padlock on the window is unlocked, click on it to lock it. Then click on the padlock again to unlock it and a prompt should pop up where you can enter your username and password. If the bug exists on your computer, you can put in any password and the padlock will unlock regardless. An editor at The Verge tested this and confirms the bug exists. We’ve reached out to Apple for a comment and will report back when we know more.