Theare used by organizations including banks and universities to add search features to Web sites. A flaw in the way the systems handle certain characters makes it possible to craft a Web link that looks like it points to a trusted site, but when clicked serves up content from a third, potentially malicious site.
"This vulnerability affects a lot of very large Web sites," John Herron, a security expert who maintains the NIST.org site, said in an e-mail. "It basically allows a virtual defacement of a Web site when following a malicious link."
The vulnerability provides cybercrooks, scams that try to trick people into giving up sensitive information such as credit card data and Social Security numbers. Phishing scams typically use with a link to a fraudulent Web site.
Google found out about the problem last week, a spokesman for the Mountain View, Calif. company said in an e-mail Monday. "We have notified all customers and provided them with clear instructions on how to protect their appliances," he wrote, adding that no Google Search Appliance or Google Mini users have reported any exploits of the flaw.
Google sent an advisory to all customers on November 22, just before the Thanksgiving holiday, the spokesman said. The vulnerability will also be addressed in the next release of the products, he said.
The cross-site scripting problem involves 7-bit Unicode Transformation Format (UTF) character encoding. "This particular vulnerability is clever because of the encoding hack," said Jeremiah Grossman, chief technology officer at WhiteHat Security, which specializes in Web application flaws and protection.
One way Internet users can protect themselves against attacks that attempt to exploit the flaw in the Google appliances is to inspect Web links. The rigged links will be very long, according to security experts.
Users of the Google appliances who have not heard from Google should contact the company for a fix. "Web site owners must be diligent about finding and fixing vulnerabilities, (since) even products supplied by well-known brands possess these extremely common issues," Grossman said.