If you have 2.8.4 your clear, and you can check if your clean by looking at the permalinks menu if anything funky has happened.
Specifically look for eval and base64_decode in there, which is the method of injection.
You can also look for a consealed admin too, you will probably need to disable javascript to tell, so firefox or opera are your friend.
If your infected, its going to be a long long night, as its infection has spread into the database, so upgrading WONT fix it.
**edited now I'm on my PC**