Samsung is now rolling another One UI beta update to the Galaxy S9 and S9 Plus users that fixes several bugs and bring features improvements. It includes the December 2018 security patch.
As the first recipient of the One UI beta test, the update is currently rolling out with build version G960/G965FXXU2ZRLF, while the size of the update is 324 MB.
If you have installed the beta build on your Galaxy S9 and S9 Plus, you can check for the update manually by heading into the Settings > Software updates > Download updates manually. This will allow the software to update and load the beta version.