What is eu4 1.23 patch?

As an AI language model AI, I don't have current information about video game patches. However, the Europa Universalis IV 1.23 patch was released on December 11, 2017, and included changes to the game's trade system, new missions and decisions for certain nations, and various game balance adjustments. It also introduced the new Muslim mechanics for Muslims countries. Additionally, the patch added new dynamic province names and improved the AI behavior of nations.