See https://github.com/tukaani-project/xz for the official repository
5.2.2 was released on 2015-09-29.
Cygwin users should note that XZ Utils 5.2.x can lose data on Cygwin 1.7.34 or older. The bugs have been fixed in Cygwin 1.7.35 and thus XZ Utils 5.2.x works correctly on Cygwin 1.7.35 and later. You can check your Cygwin version with cygcheck -V. If you cannot upgrade to new enough Cygwin, you should stick to XZ Utils 5.0.x which is fine and safe to use on older Cygwin versions.
5.2.1 was released on 2015-02-26.
Cygwin users should note that XZ Utils 5.2.x can lose data on Cygwin 1.7.34 or older. This is because XZ Utils 5.2.x can trigger certain bugs in Cygwin. These bugs have already been fixed in Cygwin CVS and thus the upcoming Cygwin 1.7.35 will be fine for XZ Utils 5.2.x. The old stable 5.0.x is fine and safe to use on older Cygwin versions.
5.0.8 was released on 2014-12-21.
The 5.0.x branch is maintained for now for those who want bug fixes without new features.
5.2.0 was released on 2014-12-21.