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://ftp.us.debian.org/debian proposed-updates main contrib non-free
to your /etc/apt/sources.list