This is an old area, you should go over here.
View the changelog for the versions of Concrete5 below.
5.4.0 Release Notes
5.3.3.1 Release Notes
5.3.3 Release Notes
5.3.2 Release Notes
5.3.1.1 Release Notes
5.3.1 Release Notes
5.3.0
Older Versions
Grab the old copies in our concrete5 archive.