If you create a login and set 'master' as default database then, the user will only be created in the master database. The login/user will not have access to any of the user/system databases untill and unless you map the user to other databases. Upon trying to access any other database it should result into the belwo error:
TITLE: Microsoft SQL Server Management Studio
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The database 'MyUserDB' is not accessible. (ObjectExplorer)
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