Please upgrade Firefox. http://www.kb.cert.org/vuls/id/714496
Vulnerability Note VU#714496 is also known as CVE-2006-5463. Red Hat issued RHSA-2006-0733 (<http://tinyurl.com/y9ejp4>) for this issue and several other issues: "Several flaws were found in the way Firefox processes certain malformed Javascript code. A malicious web page could cause the execution of Javascript code in such a way that could cause Firefox to crash or execute arbitrary code as the user running Firefox. (CVE-2006-5463, CVE-2006-5747, CVE-2006-5748) "Several flaws were found in the way Firefox renders web pages. A malicious web page could cause the browser to crash or possibly execute arbitrary code as the user running Firefox. (CVE-2006-5464) "A flaw was found in the way Firefox verifies RSA signatures. For RSA keys with exponent 3 it is possible for an attacker to forge a signature that would be incorrectly verified by the NSS library. Firefox as shipped trusts several root Certificate Authorities that use exponent 3. An attacker could have created a carefully crafted SSL certificate which be incorrectly trusted when their site was visited by a victim. This flaw was previously thought to be fixed in Firefox 1.5.0.7, however Ulrich Kuehn discovered the fix was incomplete (CVE-2006-5462) "Users of Firefox are advised to upgrade to these erratum packages, which contain Firefox version 1.5.0.8 that corrects these issues." This issue also affects Fedora Core 3.
Fedora Core 4 is now completely unmaintained. These bugs can't be fixed in that version. If the issue still persists in current Fedora Core, please reopen. Thank you, and sorry about this.