Verizon started distributing an optimized version of Google's June 2018 Android security patch to all Galaxy S9 and Galaxy S9 Plus units on its network, as evidenced by the wireless carrier's official support pages for the two devices. The Galaxy S9 is being updated with the firmware version G960USQS2ARF4, whereas the Galaxy S9 Plus is now receiving a software package identified as build G965USQS2ARF4. No bug fixes, performance improvements, or any other additions or changes are listed as being included with either update.
As is the case with all security patches distributed to Android devices, the new firmware optimized for the Galaxy S9 lineup is rolling out over the air, with its deployment starting on Thursday. The update should become available for download on a countrywide level by the end of the month. Users who still haven't received a notification suggesting they download the new files can attempt forcing a security upgrade manually through the Settings app found on their devices, i.e. its "System update" section. While the international variants of the Galaxy S9 and Galaxy S9 Plus powered by Samsung's own Exynos 9810 chip have been receiving new software in a regular manner since debuting in mid-March, their Snapdragon 845-equipped counterparts had much more issues on the support front, especially in the United States where many models are still stuck on months-old firmware.
Samsung optimizes Google's security patches for its high-end handsets on a monthly basis but it's up to its carrier partners to further tweak such updates for their particular units. Besides three years' worth of security patches, the Galaxy S9 and Galaxy S9 Plus were also released alongside a promise of two major operating system upgrades, meaning they'll eventually make the jump to Android P and Android Q. Samsung's next premium offering is scheduled to be announced later this summer in the form of the Galaxy Note 9.