As I have replied elsewhere, your account has been hacked and you must change your keys immediately - Section 3 in this post will explain how

You should then review your comments and edit or delete those that start with "Congratulations! Message from exnihilo.witness You Received 100 STEEM From exnihilo.witness".

If you don't do this, your account will continue to post a message trying to scam users and will likely result in more people downvoting and complaining to you.

Thanks in advance.