The macOS High Sierra 10.13.3 Supplemental Update fixes an issue where using certain character sequences could cause apps to crash. This update is recommended for all users.
For information on the security content of Apple software updates, please visit this website: https://support.apple.com/kb/HT201222.
You can update macOS via the Mac App Store. Please follow iClarified on Twitter, Facebook, Google+, or RSS for further updates.