The Google toolbar 1.1.58 and earlier allows remote web sites to perform unauthorized toolbar operations including script execution and file reading in other zones such as "My Computer" by opening a window to tools.google.com or the res: protocol, then using script to modify the window's location to the toolbar's configuration URL, which bypasses the origin verification check.
http://sec.greymagic.com/adv/gm001-mc/
http://archives.neohapsis.com/archives/ntbugtraq/2002-q3/0066.html