If you're a fan of Google Desktop, you may have heard about a few flaws in the suite that opened the system up to potential data theft. Revolving around a cross-site scripting exploit, it relied on JavaScript and if exploited could lead to data theft, such as passwords or documents stored on machine. Google has fixed the flaw, however, and according to the article it was a flaw that went un-exploited:

It does not appear that anyone actually took advantage of the vulnerabilities and made attacks on Google Desktop users, both Watchfire and Google said.
The search software has gained a lot of popularity due to its ability to meta-search a machine. Of course, any software that has access to every piece of data you have has to be very secure in order to be trusted. Google was extremely fast on the fix, to their credit, and hopefully they will continue to be.