Google has posted both the OTA’s and the factory images for the selected Nexus or Pixel devices. The supported devices includes Nexus 5X, Nexus 6P, Nexus 6, Nexus 9, Pixel C, Pixel and Pixel XL.
For now, we have October Security Firmware files based on Android 8.0.0 Oreo for the Pixel and Pixel XL (OPR1.170623.027, OPR3.170623.008), Pixel C (OPR1.170623.027), Nexus 6P (OPR5.170623.007), Nexus 5X (OPR4.170623.009).
Nexus 6 (N6F27M, NGI77B) and Nexus 9 (N4F27P, N9F27M) gets October security patch based on Android 7.1.1.
Note that for the Google Pixel, OPR1.170623.027 is for Project Fi and Canad, while OPR3.170623.008 is for everyone else.
You can grab Factory Image or OTA file at the links below.
Links: Factory Image | OTA File