Today, my friend and teammate jiangshibiao was going to register for the round, but discovered that his Codeforces account was hacked and the avatar as well as the password has been changed. The email could be changed too, but he is unsure right now. I looked at the avatar and immediately noticed it was the same as [user:[user:im0qianqian],2018-08-27]'s avatar, who made a blog post about his account being hacked too.
I think probably the same hacker did it, and there may be more victims. So I would like to invite MikeMirzayanov to look into the issue and possibly help my friend get his account back. Also, I would advise users who have weak passwords to change the password immediately.
Also, jiangshibiao and me are onsite at Petrozavodsk Camp right now, so maybe someone can meet him in person if needed to verify his identify.
UPD Aug. 29:
The hacker sent me a message in Chinese with the account of im0qianqian claiming that he changed the password and the email back. Then im0qianqian sent me another message saying that he got his account back and the previous message wasn't sent by him. Unfortunately, my friend jiangshibiao tried the original password but it still does not work, and he forgot what email address was used when registering his account. Therefore he is still locked out of his account. Any help from Codeforces administration is still greatly appreciated.
UPD2: Apparently the hacker did not really change the password and email back, as the "last visit" of jiangshibiao is two days ago.
It seems that I caused a big trouble for you.
I changed the password and the email of your account back.
by Hacker (As a reminder, you password is too weak, I suggest you change it)
UPD Aug. 31:
The hacker changed the email back and my friend got back his account. Thanks everyone who replied in the post.