If you have not done anything to protect your WordPress site, most probably you are not safe. By default, WordPress only comes with a single login mechanism. Anyone that has your username and password can easily login to your site and wreak havoc. The only way to prevent it is to tighten the security of your site so other people won’t be able to crack into your site easily.
IE8 Beta is gone and hopefully replaced by an improved RC1. A browser capable of remembering passwords doesn’t seem like too much to ask. With any luck at all the tabbed browsing and other improvements will be worth while because the browser will be able to render pages and do the small things that so far have escaped recent Internet Explorer releases.