The primary objective of the release is game security. Because the official master servers lack ongoing support, old game builds are exceptionally vulnerable to malicious scripts.
Call of Duty: Mobile recently released its update, titled "Final Snow." If this is the game you are asking about, here are the patch notes highlights for the update (often referenced as version 21.x): call of duty 4 modern warfare update 21.1
Unlike official patches deployed by Infinity Ward or Activision during the game's commercial prime, this update keeps the original game alive for modern competitive loops. Key Takeaways of Update 21.1 The primary objective of the release is game security