https://support.abp.io/QA/Questions/131/Bugs--Issues-v2.6.2#answer-544beea9-dc28-0b41-1637-39f4cb588d7c
Steps to reproduce:
Go to Administration > Settings > Identity management > User Settings
Uncheck these two options
Email update enabled
User name update enabled
Save
Go to Identity management > Users
Edit a user
.