Unintended creation of new custom fields, resolutions and users by non admin users during migration

[Priyanka Desai]

I have seen when a user migrates data to Jira, it auto creates custom fields, resolutions and users that are not in JIRA. Being an admin, this is concerning to my team as a normal user can create custom fields leading to performance issues. Basically this happens when the data being migrated has the values that JIRA does not have. Any solution? 

[Steven F Behnke]

This should only occur when using the Import Tool, which is admin only. The user-facing CSV import tool, in the Issues Menu, doesn't allow you to create values or fields.