A number of vulnerabilities were discovered in Mozilla 1.4:
A malicious website could gain access to a user's authentication credentials to a proxy server.
Script.prototype.freeze/thaw could allow an attacker to run arbitrary code on your computer.
A vulnerability was also discovered in the NSS security suite which ships with Mozilla. The S/MIME implementation would allow remote attackers to cause a Denial of Service and possibly execute arbitrary code via an S/MIME email message containing certain unexpected ASN.1 constructs, which was demonstrated using the NISCC test suite. NSS version 3.9 corrects these problems and has been included in this package (which shipped with NSS 3.8).
Finally, Corsaire discovered that a number of HTTP user agents contained a flaw in how they handle cookies. This flaw could allow an attacker to avoid the path restrictions specified by a cookie's originator. According to their advisory:
"The cookie specifications detail a path argument that can be used to restrict the areas of a host that will be exposed to a cookie. By using standard traversal techniques this functionality can be subverted, potentially exposing the cookie to scrutiny and use in further attacks."
As well, a bug with Mozilla and Finnish keyboards has been corrected.