What's the issue?
The owner of the database is unknown, meaning you likely restored this database on an instance where the owner login does not exist.
Why is this a problem?
This isn't so much a problem as a mess that should be cleaned up, as you don't know what kind of permissions will be assigned if you restore a backup of this database on an instance where the login does exist.
What should you do about this?
We recommend you have databases owned by the sa login, since that login exists on every instance and is correctly a member of the sysadmin group with necessary permissions.
You can change the owner a database with this T-SQL, replacing DatabaseName with the name of the database.
ALTER AUTHORIZATION ON DATABASE::YourDatabaseName to sa;
If you need to execute this, do so during periods with less activity as there is a chance it could cause some momentary blocking.
Vulnerability
Category
What do the Vulnerability Levels mean?
0 - Information only. This is stuff you should know about your instances like version and service account used, but if you don't know it…well, now you do.
1 - High vulnerability requiring action. These are the issues that could most likely lead to your company being front page news for all the wrong reasons. If your instances have any results at this level then we recommend cancelling that 3-martini lunch and instead huddling with your team to figure out when to address these issues.
2 - High vulnerability to review. These include settings and assigned permissions you should review soon, if not immediately. These findings may not necessarily indicate a clear vulnerability, but we've found unexpected vulnerabilities in these categories at many, many clients.
3 - Potential vulnerability to review. These are configurations or assigned permissions you may be using that could lead to problems for users. Or maybe they're just required for your applications. Either way, we recommend reviewing these to make sure these are correct.
4 – Low vulnerability with recommended action. These are typically security inconsistencies that should be addressed. They aren't likely to cause problems, but you should clean up the mess.