I faced a issue that customer groups(not logged in)are created by unidentified event automatically.
And we have multiple store but in specific store, it appear. I blocked the function that unlogged customers allow to buy products but i guess it is not reason bc it has been created since i deleted the function.
Do you guys know why this situation happened to me?
This issue is caused by 3rd party extension, if we turn off the possibility that your store is compromised. It further means that you either have an extension which makes this issue (which I doubt), or you have some custom code and development which is causing this. In that case, no one can help you about it without looking into your code base, so you better find Developer to investigate that for you.