There exist two seperate security issues in Mozilla Firefox concerning 
JavaScript prompts appearing from domain which is not the true origin. 
The first is about spawning JavaScript prompted message over web page of 
another domain, so in effect, the address bar and the browser content 
are from one domain, but the prompted JavaScript message is generated by 
script from another different domain. This is resulted from a race 
condition scenario, in which the browser is first navigated to URL of 
another domain, then before it's loaded, immediately launch JavaScript 
message prompting, so JavaScript message is displayed over a web page 
other than its origin web page. The issue here only affects Firefox, and 
doesn't seem to affect Internet Explorer and Google Chrome. This is 
CVE-2009-4129. The second is regarding the function named 
"MakeScriptDialogTitle"(in file "nsGlobalWindow.cpp" of Firefox source 
code), responsible for "Script Dialog Title", which is designed to show 
"host". The "MakeScriptDialogTitle" function removes usernames and 
passwords from URL, with a purpose of "spoof prevention", but it's not 
enough, because script dialog has limited and predictable width, so only 
the prefix will be displayed if domain name is long. This is 
CVE-2009-4130. Topsec has the credit.