Multiple vulnerabilities have been reported in Netscape, which can be exploited by malicious people to bypass certain security restrictions, gain knowledge of sensitive information, conduct cross-site scripting attacks, or potentially compromise a user's system.

See vulnerabilities #1, #2, #6, and #7 for more information:
SA24205

The vulnerabilities have been reported in version 8.1.2. Other versions may also be affected.

Solution
Do not browse untrusted sites and disable Javascript.
Original Advisory
http://www.mozilla.org/security/announce/2007/mfsa2007-02.html
http://www.mozilla.org/security/announce/2007/mfsa2007-03.html
http://www.mozilla.org/security/announce/2007/mfsa2007-06.html
http://www.mozilla.org/security/announce/2007/mfsa2007-07.html

Other references
Further details available in Customer Area

Deep Links
Links available in Customer Area