Where are the schema change logs of Jira core and Jira Software cloud based?

[Shawn]

We found that our project settings have been changed by someone, such as a notification scheme and a flowchart scheme. But none of us have changed. We want to find logs to see who and when these changes occurred. But we couldn't find any logs. We want to know if someone's login credentials have been hacked.

Urgent. Thanks!