Mozilla Firefox 2.0.0.9 allows remote attackers to cause a denial of service (CPU consumption and crash) via an iframe with Javascript that sets the document.location to contain a leading NULL byte (\x00) and a (1) res://, (2) about:config, or (3) file:/// URI.

More... (http://nvd.nist.gov/nvd.cfm?cvename=CVE-2007-5896)