A random wall in Katowice/Poland or a statement? You never know where they will start to work but they will do it. As a fine example Escif (the group which is doing that) is claiming itself that they are not an artist or a group of artist.
“Escif is a situation that involves a lot of people. Not just those that creates these mural paintings and works but also everybody who try to understand it.”
Further information can be found on the website