After a standard system upgrade you need to restart Firefox to effect the necessary changes.
Kojima Hajime discovered that Firefox did not properly handle an escaped null character. An attacker may be able to exploit this flaw to bypass script sanitization. (CVE-2008-5510)
Wladimir Palant discovered that Firefox did not restrict access to cookies in HTTP response headers. If a user were tricked into opening a malicious web page, a remote attacker could view sensitive information. (CVE-2009-0357)