Sprint has released a new software update G950USQU1AQJH for Galaxy S8 and update G955USQU1AQJH for Galaxy S8 Plus. The latest update has fixed the KRACK wifi issue.
In addition, the update comes with Android October Security patch which addresses Common Vulnerabilities and Exposures (CVE) in the open-source Android OS. Additionally, there are minor bug fixes and general performance improvements also. The patch size is around 377 to 386MB.
Software update G950USQU1AQJH for Galaxy S8 and update G955USQU1AQJH for Galaxy S8 Plus will gradually release to everyone. You can also check manually for updates, go to Settings > About device > System update.
Make sure you have enough charge on your device at least 60% to 70% before downloading the update.