Hi,
There is no easy way to find out what changes were made by a user. However, you can refer to a few things and can figure it out.
The CUCM security log will have info on user accesses. This is provided your users use their userid to log in and not a common user id.
As for changes made, I don't suppose there is a log for that. However, the CCMAdmin web page logs will tell you the webpages accessed. You can get the logs/traces using RTMT.
