Debian is committed to providing security updates to the stable distribution as quickly as possible, but we also need time to thoroughly test such updates to ensure that they meet our high standards. Updates to stable are placed in this directory, dists/proposed-updates. After testing, and possible bug-fixing, a new release of the stable distribution is made which includes them. You can access this directory with apt by adding deb http://ftp1.us.debian.org/debian dists/proposed-updates/ to your /etc/apt/sources.list