In five minutes anonymous has made 54 changes https://ru.wikipedia.org/w/index.php?title=%D0%92%D0%B8%D0%BA%D0%B8%D0%BF%D0%B5%D0%B4%D0%B8%D1%8F:%D0%9F%D0%B5%D1%81%D0%BE%D1%87%D0%BD%D0%B8%D1%86%D0%B0/Flow&limit=100&action=history
1)to undo his actions have to do again 54 actions
2)he changed the topic title - (from "Horror..." to "") - it turned out that this cannot be undone. When the topic title not in English, for example Russian, in the field "from" fit smaller number of letters. If the topic name is long, it is not entirely fit - " from "Horror..." ". In the history page the line has a buttons "solved" and "hide", but there is no button "cancel" - thus the last part of the title of the topic is lost forever!
3)you can unhide the answer, but but cancel is not working as expected - it turns out that I'm getting a new author as the last editor for summary, for the posts of other users, and so the theme goes up. And it says that I've changed it, although I wanted only to undo the vandalism, returning back the old dates and text for last the real authors of the text. Expected that the cancel will return the oldest date and the previous value of the "last changed text was the user".