This indicates a possible attempt by an attacker to exploit an "Iframe" size vulnerability in Mozilla Firefox. This is due to the application's failure to properly handle overly large size attributes in the "Iframe" tag. A successful exploit may cause the browser to crash via a specially crafted "Iframe" tag on a malicious web site, resulting in a denial of service.
Mozilla Firefox 1.x
Denial of Service.
Upgrade to Mozilla Firefox 1.5 or higher.