Argument injection vulnerability in Microsoft Internet Explorer, when running on systems with Firefox installed and certain URIs registered, allows remote attackers to conduct cross-browser scripting attacks and execute arbitrary commands via shell metacharacters in a (1) FirefoxURL or (2) FirefoxHTML URI, which are inserted into the command line that is created when invoking firefox.exe.  NOTE: it has been debated as to whether the issue is in Internet Explorer or Firefox. As of 20070711, it is CVE's opinion that IE appears to be failing to properly delimit the URL argument when invoking Firefox, and this issue could arise with other protocol handlers in IE as well. However, Mozilla has stated that it will address the issue with a "defense in depth" fix that will "prevent IE from sending Firefox malicious data."