What is a Debian Security Advisory (DSA)?
It is information sent by the Debian Security Team (see below) regarding the discovery and fix for a security related vulnerability in a package available in Debian GNU/Linux. Signed DSAs are sent to public mailing lists (debian-security-announce) and posted on Debian’s web site (both in the front page and in the security area). DSAs include information on the affected package(s), the security flaw that was discovered and where to retrieve the updated packages (and their MD5 sums).