You can safely update to 1.18.1, as it's backwards compatible with 1.18.
Note on security: Our network is running 1.18 for now, but with the security fix from 1.18.1 back ported.
Simply put: UPDATE YOUR GAME CLIENT TO 1.18.1 AND JOIN AS USUAL! :D
Edit 2021-12-17: The network is now updated to 1.18.1. For those of you wondering, yes, the earlier announcement about "a security fix" was indeed about Log4j.