-snip-
Was it a different "blockchain" wallet?
Or are you certain of what happened (because it's been 8 months since based from the timestamp)?
Yes, I was wrong
This transaction was done from the site
https://freebitco.in/?op=home, which was the total inventory of this site
This happened after I sent some bitcoins from this site to another site. Is it possible that this site hacked my account address?
But the hacker also had access to my blockchain account and entered it because a confirmation email was sent to me, but fortunately I had no money in the blockchain.
If you're positive that it's the exact URL that you've been using, then it's legitimate and probably won't hack your balance.
For the hacker, he also got the email password so it's pretty easy to withdraw from freebitco(in) if you didn't set 2FA on.