Dear @luka_hajnrihar ,
the "(auth skip user)" is nothing MWG write by default. However, you have the ability to write dummy user such as "(auth skip user)" into variable Authentication.UserName. Whatever the value is will be logged to Access log and gets to the database.
You can use search function in the UI to find above mentioned Property "Authentication.UserName" usage in your Rule Set. Which can help you understanding when it is been set.
Best Regards,
Sergej
If you find this post useful, Please give it a Kudos! Also, Please don't forget to select "Accept as a solution" if this reply resolves your query!