A new software upgrade is hitting AT&T Samsung Galaxy Note 8 units across the States. Weighing in at between 377MB - 386MB, the update should bump the software version of Samsung's high-end phablet to N950USQU2BQJA.
After installing the new version, users will be safeguarded from a couple of dangerous security vulnerabilities. The update includes the Android security patch for the month of October and fixes for both the KRACK Wi-Fi and BlueBorne exploits.
Aside from that, enhancements to network performance, stability, and other various updates and fixes are also mentioned in the changelog. The update is available OTA, but it might need some time to reach all compatible devices. You can check for it manually by going to Settings > About Device > Software Updates.
As always, make sure that your phone is sufficiently charged and connected to a Wi-Fi network before proceeding with a patch of this size.