Steemcleaner is a bot which can detect the plagiarized blog you had post.
Steemcleaner can be flagged by two ways such as
1)you have done plagiarized from the website and directly post on the steemit and so Steemcleaner had detected the lost for you from website and so he had given you a flagged on your post.
2)sometimes mistakes done by Steemcleaner so we can go to discord and we give evidence or proof and tell them that you don't done any plagiarism and so they will remove the flagged given my Steemcleaner.
So don't worry about flagged which given by the Steemcleaner if our fault is not there we can discord it and if we are having plagiarized and also they give think and then we can't able to discord that so for that we have to stop doing copy paste work on such a big platform