Ubuntu announced the release of 5.10 almost 18 months ago, on October 13th. As with the earlier releases, Ubuntu committed to ongoing security and critical fixes for a period of 18 months. The support period is now nearing its end and Ubuntu 5.10 will reach end of life on Friday April 13th 2007. At that time, Ubuntu Security Notices will no longer include information or updated packages for Ubuntu 5.10.
The supported upgrade path from Ubuntu 5.10 is via Ubuntu 6.06 LTS. Instructions and caveats for the upgrade may be found at https://help.ubuntu.com/community/DapperUpgrades. Note that upgrades to version 6.10 and beyond are only supported in multiple steps, via an upgrade first to 6.06 LTS, then to 6.10. Both Ubuntu 6.06 LTS and Ubuntu 6.10 continue to be actively supported with security updates and select high-impact bug fixes. All announcements of official security updates for Ubuntu releases are sent to the ubuntu-security-announce mailing list, information about which may be found at https://lists.ubuntu.com/mailman/listinfo/ubuntu-security-announce.