Hacking
 

Is it possible to hack the vbulletin forums or the cpanel or the FTP without knowing a password and username of either?

I would say that it is quite impossible.

Are you positive?

Well, I'm not sure if there are tools avaliable to hackers (probably are) But I'm pretty sure you cannot "guess" your way into all three.

If a member trys to access the vBulletin ACP they will just get a password protected box, they would have to know the address of your cpanel to start with, then they would have to guess your username which is pretty hard to do as it can be anything and they would have to guess your password, which is very unlikely to happen, same with the FTP, they would have to know either the ftp address or the server ip and your FTP username/ pass which, again would be hard to guess.

I agree with mikey,the front door is closed as with all his examples with the exception of the ftp
most hacking tools will look at the back door of your ftp,and if it's open no username/password is required.

It's quite impossible to hack ftp/cpanel, but it is possible to hack vb or user's account.

If someone can hack your FTP access, then you need to have a chat with your host.
If someone can hack your Vbulletin accounts, then report it to Vbulletin and they'll get a fix out ASAP.

I think it's safe to say there's no known issues, otherwise, it'd be discussed heavily.