Most Websites harbor at least one major vulnerability, and over 80 percent of Websites have had a critical security flaw, according to new data released today by WhiteHat Security.

The Website vulnerability statistics, based on Website vulnerability data gathered from WhiteHat's own enterprise clients, show that 63 percent of Websites have at least one high, critical, or urgent vulnerability issue, and there's an average of seven unfixed vulnerabilities in a Website today.

"What we know from this report is that the Web is at least this insecure," says Jeremiah Grossman, CTO of WhiteHat.

The top ten classes of vulnerabilities hasn't changed much from WhiteHat's findings in the fourth quarter of 2008. The pervasive cross-site scripting (XSS) flaw still leads the pack as the most likely vulnerability in a Website, with a 65 percent chance that a Website has XSS bugs, followed by information leakage, with 47 percent.

And the average number of vulnerabilities per Website over its lifetime is 17, according to WhiteHat's data.

"Customers are fixing large swaths of vulnerabilities, but it's really tough to wipe out 100 percent of vulnerabilities, even by class and severity," Grossman says. "And even if you fix nine of 10 cross-site scripting vulnerabilities, you still have one. That's why the percentage of sites likely to have cross-site scripting vulns is" so high, he says.

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