This is a point release with bug fixes and a language update. v12.0 was a significant upgrade that includes updates to various packages and use of .NET 4.5.1, as well as MVC 5.
There are no changes from v12.0. For other versions, this release has data changes. Run the PopForums9.2andLaterto12.0.sql script against your database, which is found in the PopForums.Data.SqlSingleWebServer project.
None at this time.