XULRunner 126.96.36.199 is the first stable developer preview release of XULRunner. It features include lauching standalone XUL applications and embedding APIs. This can be used for rendering web pages within native and java applications.
Is a security/stability update which is available as a patch to be downloaded. It replaces version version 188.8.131.52. All XULRunner users should upgrade. This patch can be found at the Mozilla Development Center under XULRunner 184.108.40.206 Release Notes