First of all, do not panic. All the activity to remove funds from your account requires multiple confirmations (email link + 2FA for withdrawing BTC, for example), so if your account security was properly set up, it would be almost impossible to do damage to you.
If you believe your account got hacked:
Notify the support team via chat about the hack.
We will freeze the account making it inaccessible to anyone.
Make sure your email account has no unauthorized sessions open, reset passwords and 2FA on your email.
Confirm that your email is secure and provide all the necessary information to unfreeze your account.
After the account is unlocked, reset your password and 2FA immediately.
CEX.IO support will investigate this issue.
Since all important actions on CEX.IO account require an email and/or 2FA confirmation, we will need to check the email address associated with this account.
We will collect information on the unauthorized events (IP and timestamp) and forward it to you for further investigation by your local authorities.
CEX.IO is not responsible for your personal email account breach.
CEX.IO staff will provide assistance to determine the identity and location of the hacker and will take all actions possible, to return any lost funds to the owner.