Search engine darling Google has patched a hole in its search engine the could have allowed malicious hackers to modify the content of the Google search results page or silently modify search results, but a new hole may have already appeared.

The vulnerability concerns the Google Custom WebSearch service, which allows third-party Web portals and other Web sites to use Google's servers to search content on their Web site. A flaw in Google's Web servers allowed malicious hackers to insert Javascript instead of links to image files, allowing them to alter the appearance of the Google search results page or steal search data. After being alerted to the hole, Google fixed the vulnerability, said Nathan Tyler, a Google spokesman.

"Google was recently alerted to a potential security vulnerability affecting users of our Web site. We have since fixed this vulnerability, and all current and future Google.com users are protected," Tyler said.

The company is also aware of a second vulnerability, discovered by U.K. security firm Netcraft and will be fixing its systems shortly to remove the vulnerability, he said.

The Custom WebSearch vulnerability was first reported in the online security newsgroup Bugtraq. Google's servers fail to validate URLs for image files to make sure they actually point to images. Malicious hackers could trigger the vulnerability using a Google custom search form, or even through a customized HTML link, by feeding Google's servers computer script instead of an image URL, according to the notice's author, who used the name "Jim Ley."

According to the notice's author, the vulnerability has existed for around two years without being fixed by Google, which was notified twice of the hole. The recent release of a desktop search tool from Google worsened the impact of the flaw, allowing hackers to leverage the Desktop Search feature to search for and steal content, such as passwords or personal financial information, from files on the local hard drive.

A number of major Web sites use the Google Custom WebSearch service, including Netscape Communications Corp., The Washington Post Co. and Virgin.net, according to Google's Web page.

In another example of how the flaw could be used, Ley posted a link on his Web site that replaced Google's main page with a page announcing that Google was becoming a for-fee search service and asking visitors to provide credit card information to sign up for the service.

The IDG News Service is a Network World affiliate.