I am not sure to be honest. But once, there was a case that someone got Denial of Judgement and unfairly made him lose rating and he shouldn't. He wrote a blog about that but I don't remember it so I won't be able to get it though. They rolled back rating changes and rejudged his solution and then re-published rating changes. But Denial of Judgement is a very rare case and I don't think that rolled back changes is from it. There might be other possibilities like:

• A cheater was caught late after rating changes

• Innocent person copied a code from the same source(for example GeeksForGeeks) and lead him to get disqualified due to cheating although he didn't cheated(In this case, he proves to codeforces administrators that he is innocent by giving them enough proof)

• Rating changes didn't change Rank of the person(happened only once last year I think)

I am not sure what else would cause rating changes to roll back to be honest. But this is all the information that I have.

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No such comment for this contest but I'm assuming it's becoming a common practice nowadays.

Auto comment: topic has been updated by ajit (previous revision, new revision, compare).

I am willing to wait even till the next context if it means they will catch all the cheaters. They have reduced the meaning of hard work, patience and skill to nothing.

I have never cheat but the CF rolled my all scores back You know, that my level is really low, and i can't do most questions in those contests But I 've never cheat. I don't know the reason why they rolled my scores back.