Periodically, we get questions about what to do when someone vandalises their question, or even someone else's question. Here I have compiled a list of these questions so that this kind of question does not get asked again.
The list:
What is the policy for users who deliberately vandalise their own posts?
Questions edited in such a way that they cannot be recognized
What can moderators do when a user defaces his/her own post?
Does that count as defacement?
On the response to self-vandalised questions
Vandalizing question posted by others
Also related:
Defacement/Censorship of peoples answers
Why was my suggested edit rejected?
Is it within policy for instructors to edit post text to remove questions from active exams?