I never keep very much money in online wallets. All it takes is the site to make up a hacker story about why your bitcoins are gone and you are out.
That's not partially true. Since all online wallets have their own security measures. You'll just need to to confirm everything they asked to tighten up your security, having multiple layers of your accessibility as well as its security.
The only reason why it is vulnerable is that, you didn't do what they're asking for you to do. To tighten it up, and the hackers could only cracked because its easy to have access over it, since it doesn't have multiple layers of security.