Really the DAC doesn't really add any security implications. Only sysadmins can connect and if you are a sysadmin you have complete control of the instance anyway. The only thing you can do in the DAC that you can't in a regular connection is view the system tables. This can give you a little bit of extra information (the password hash for a contained user for example) but nothing that is all that big a deal if you are a sysadmin already.
That being said, you still want to make sure your sysadmins are under control 🙂
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