This indicates an attack attempt to exploit a Content Injection Spoofing vulnerability in Mozilla products.
This issue is caused by an error in the vulnerable software when handling a web page with an invalid url that is passed to "document.location". It may allow remote attackers to execute arbitrary code by sending a crafted web page.
Mozilla Firefox before 3.0.16 and 3.5.x before 3.5.6
SeaMonkey before 2.0.1
Refer to the vendor's web site for suggested workaround.