Steam accounts can be compromised, usually through a fake Steam login page. We have more information about this here.
If you believe your Steam account has been compromised and, in turn, your account on the site, it's important you take action quickly. You can follow these steps to secure your account:
To kick this person off your account you must go to this page and click 'Deauthorize all other devices'.
Change the password on your Steam account. Click here to see how.
Go here and click "Revoke My Steam Web API Key". (If there is nothing there, don't worry about this step)
Create a new Steam Trade URL here.
We also recommend that you log out of CSGOEmpire using the "Logout from all devices" option (in case scammers have logged in using your Steam account), and log back in.
Once you've completed these steps, anyone who did have unauthorised access to your account would no longer have access. This is also why we recommend setting up TFA on your Empire account to keep your coins safe even if your Steam account is compromised.
Our support team will be happy to help and investigate any issues you face in regards to your account's security too.