Netscape has a long-standing problem of always being late with Firefox patches but, with this update, it's clear that AOL is making the effort to keep pace with fixes from Mozilla. Netscape is basically a wrapper around Firefox and Microsoft's Internet Explorer.
The Netscape update (available for download here) fixes several bugs that could lead to cross-site scripting, cross-site request forgery and other system compromise attacks.
Secunia flags this as a "highly critical" update.