Hi guys,
Just wanted to mention that this happened to me as well and I am not a Marketplace seller. My account was compromised early Saturday morning and Epic was quick to act, restoring my account by Monday morning. If you have any doubts I recommend you change your password immediately and (if you want to be extra careful), delete your saved CC number for now, just in case.
The folks that accessed my account purchased several assets with my card and then changed the email associated with this account. This was solved quickly by contacting the Epic help email (help@epicgames.com)
I do want to commend the support team for getting this fixed ASAP and hope we can get two-factor authentication soon 