If macOS High Sierra shows your password instead of the password hint for an encrypted APFS volume
Take steps to protect your data if you see your password instead of your password hint for an encrypted APFS volume.
Your password might be displayed instead of your password hint if you used the Add APFS Volume command in Disk Utility to create an encrypted APFS volume, and you supplied a password hint.
Changing the password on an affected volume clears the hint but doesn’t affect the underlying encryption keys that protect the data.
If you have this issue, Apple has released a supplementary update. Please update your OS immediately.
See https://9to5mac.com/2017/10/05/apple-releases-supplementary-update-for-macos-high-sierra-with-various-bug-fixes/ for more information
Encrypted APFS volumes that you created using any other method are not affected.
Read more https://support.apple.com/en-us/HT208168