What's the issue?
There is no issue. This is simply the name of the account used by the SQL Server service.
Why is this a problem?
This probably isn't a problem, but did you know this was the account used to run this service? If not, you probably want to note it and any permissions it is assigned in case you need to restore this instance and all it's databases on another server.
What should you do about this?
You probably don't need to take any action other than documenting this information, but we strongly recommend you consider using a group Managed Service Account (gMSA) for your SQL Server service. Using a gMSA provides great benefits such as automatically changing the password, simplified service principal name (SPN) management, and security from being used as a login by those with bad intentions.
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.