Unknown versions of Mozilla allow remote attackers to cause a denial of service (high CPU/RAM consumption) using Javascript with an infinite loop that continues to add input to a form, possibly as the result of inserting control characters, as demonstrated using an embedded ctrl-U.
The Javascript "Same Origin Policy" (SOP), as implemented in (1) Netscape, (2) Mozilla, and (3) Internet Explorer, allows a remote web server to access HTTP and SOAP/XML content from restricted sites by mapping the malicious server's parent DNS domain name to the restricted site, loading a page from the restricted site into one frame, and passing the information to the attacker-controlled frame, which is allowed because the document.domain of the two frames matches on the parent domain.