Microsoft Corporation has announced a potential security problem affecting Internet Explorer that could enable a Web site operator to access the contents of your local disks. Dubbed the "cross-frame navigate" issue, the problem affects both Windows and Macintosh versions of Internet Explorer 3.x and 4.x. On the Macintosh, Internet Explorer 3.01, 4.0, and 4.01 are vulnerable although Explorer 3.0 is not; under Windows, any application (such as Eudora Pro) that can use Explorer’s HTML engine could also be vulnerable. Microsoft has released a 2.3 MB updater for the Mac version of Internet Explorer 4.01 that fixes the problem; users of Explorer 3.01 and 4.0 must upgrade to version 4.01 and then apply the patch. Although little additional information is available, Microsoft claims there are no reports of would-be hackers exploiting this loophole.