xF2 Add-on [MMO] Impersonate User 2.3.0

You can upgrade from this add-on Unmaintained - Login as User. When updating a resource, all necessary and old add-on data is transferred to your forum.
This add-on gives privileged users the ability to login as any other user on the forum (as long as they're not whitelisted).
Key Features:

• Permission controlled - choose who can login as another user
• Whitelist - define users that cannot be logged into by others
• Make users supply a reason when logging in as another user
• Send a conversation when logging into another user
• Doesn't cause your IP to be logged with the user being logged into
• Alerts, conversation, threads are not marked as read.
• All logins are logged to the moderator log