When September’s Android security patch went live last week for most Nexus and Pixel devices, the Nexus Player’s files were not included. In fact, no Android 8.0 “Oreo” images had been posted by Google for their Nexus Android TV unit up until a few minutes ago. That has now changed and you can grab Oreo factory image and OTA files for the Nexus Player, with September’s security patch as build OPR6.170623.021.
The image or OTA files are available at the links below. For instructions on how to flash a factory image, here you go. For instructions on how to flash an OTA .zip file, here you go.