Firefox before 1.0 and Mozilla before 1.7.5 allow inactive (background) tabs to focus on input being entered in the active tab, as originally reported using form fields, which allows remote attackers to steal sensitive data that is intended for other sites, which could facilitate phishing attacks.
Mozilla 1.5 through 1.7 allows a CA certificate to be imported even when their DN is the same as that of the built-in CA root certificate, which allows remote attackers to cause a denial of service to SSL pages because the malicious certificate is treated as invalid.
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.