That seems to be a hacker's address.
It is very possible that if your password for Poloniex was simple, that it was easily hacked.
If you did not receive the withdrawal confirmation email, it is possible that the hacker changed you email contact.
If you still have access to your account currently (hacker did not change your password), it is possible that it is really malware.

You should scan your computer for viruses and malware immediately.

Did you open a support ticket? If so, please advise what their explanation was?