All facts point out that the Snapdragon 835+ (SM-G955) powered US version of the
Samsung Galaxy S8+ has just been rooted.
SuperSU running on the Galaxy S8+
Being such a high-profile and popular handset, one would probably expect avid developers and Android tinkerers to have cracked the system gates of the Snapdragon-powered
Galaxy S8+ long ago, but sadly, this was not the case until recently, when XDA user
BotsOne announced in the main XDA root thread for the device that root access has been successfully gained, and subsequently, SuperSU has been installed on the device. With the
Galaxy S8+ successfully rooted, the XDA hive mind is about to move its attention towards the smaller Snapdragon-running
Galaxy S8 (SM-G950).
However, the root was achieved thanks to an exploit that did not allow the team to unlock the bootloader of the Galaxy S8+. Essentially, this means that adventurous tinkerers won't be able to flash TWRP or another custom recovery on the phone just yet.
As far as the Exynos-powered versions of the Galaxy S8 (SM-G950F) and S8+ (SM-G955F) go, their users are a tad luckier - both phones have been successfully rooted and have unlockable bootloaders, which opens the possibility for custom ROMs.