i had a wallet before in there i have same problem
probably you make backup and someone use your backup wallet
make new wallet or use electrum or bitcoincore
Overall wallet server not at all as my knowledge but the each wallet will be able to hacked with the public address with the verified password you have done with the pushed e-mail confirmed. This is happend to many people and their wallet alone indidually hacked bro.
If you do not want to hack the wallet you please always use the correct URL and don't connect any VPN while you are logging in to it. Especially do not use the Google seach like blockchain and goes to the first suggested link at there.
I am sure I was using the right URL to access my blockchain.info account online because each time it brough up my account balance info.
Could someone be able to access my wallet knowing the 4 digits passcode on my iPhone wallet app (not the password to my account)?