Just like to bump this, exact same thing happened to me after using
https://bitcoinvanity.appspot.comI imported the new address into blockchain.info and secured with 2FA and email login approval. 7 BTC lost withdrawn to a random address over the past weekend.
It may sound a bit harsh but it's your own fault. I have advised a legit, secure and good working vanity pool above...
I don't know how legit bitcoinvanity.appspot.com is, but it doesn't seem secure if you ask me. You don't need to create extra randomness to get a vanity address. I don't even know how that would help.
I do feel bad for you. Losing 7
BTC sucks.
I realise that and the loss of 7 BTC has been an expensive lesson. Hopefully this is a warning to others, would be nice to be 100% certain that it is due to that website that I have lost the coins though
My bet would be on the vanity site you used, because your other wallets are fine.