A user was created and deleted on your server with the name cldiaguser. You may receive a notification if running the third-party software CSF or see the following in your system's secure logs.
[06:00:00 server root ~]cPs# grep -i cldiag /var/log/secure
Jan 13 05:35:05 server useradd: new group: name=cldiaguser, GID=1121
Jan 13 05:35:05 server useradd: new user: name=cldiaguser, UID=1000, GID=1121, home=/home/cldiaguser, shell=/bin/bash
Jan 13 05:35:10 server userdel: delete user 'cldiaguser'
This user was created by the Cloudlinux cron task for the cldiag tool. This change in behavior was an intentional change in the package update for package lve-utils in version 4.2.25-1. The Cloudlinux team has been made aware of the potential notifications.
This was an expected change made by the Cloudlinux team. If you are receiving notifications from third-party software you can either exclude this user or disregard/filter emails relating to this change. Please note that this cron runs once per day and will be expected to create/remove a user each time after this update.