The SQL injection flaw could have allowed attackers to access the 32 million entries of user names plus passwords in the Rockyou.com database - and since the user names and passwords are by default the same as the users webmail account—such as Hotmail, Yahoo or Gmail—this is a major lapse in security.
An attacker can use these credentials to perform any of the following actions:
1. Extract private information from the inbox: credit card numbers, confidential business information, passwords to another application such as bank application embarrassing pictures etc.
2. Identity theft – The attacker can send mail to the victim’s entire contact list on behalf of the victim.
3. Harvest the contacts info for spam – if each account has 10 unique contacts then the spammer will have 300 million addresses to spam.
"We have notified the site operators of this problem, who re-acted quickly and fixed the issue over the weekend. Unfortunately some accounts had already been compromised before the vulnerability was fixed. All users need to be cautious and ensure they change their email passwords as their credentials may have been put at risk” said Amichai Shulman, Imperva CTO.