Cross-Site Scripting

More web sites are vulnerable to cross-site scripting (or XSS) attacks than any other type of web application attack. According to statistics from the Web Application Security Consortium (WASC), almost 40 percent of all web applications tested for security flaws have at least one XSS vulnerability. Two additional separate studies by WhiteHat Security and Cenzic Inc. showed even greater percentages: Seventy percent of the sites they surveyed were vulnerable to XSS attacks. There’s no way to know how many web sites really do have XSS holes, but no matter what that number really is, it’s definitely too high for comfort.

As well as being the most prevalent web application vulnerability, XSS has another dubious honor, in that ...

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