The Houdini 18.0 production build on Steam (including the games backport) has been updated to 18.0.499.
You can view information about the Houdini 18 Backport here.
You can view the changelog here.
You can access different Houdini Indie production builds and daily builds on Steam by following these steps:
-Right click on Houdini Indie in your Steam library
-Select Properties
-Select the Betas tab
-Choose the Houdini daily build or production build you want to use from the betas list.
(Select "None - Opt out of all beta programs" to use the most current production build)