Following an uncharacteristically messy rollout of the September Android Security Update that took a while to be fully distributed, Google seems to be returning to its standard software release practices this month and has debuted the October security patch for Android devices alongside its factory images, as well as full OTA files. The software packages launched by the Alphabet-owned company were made for the Pixel, Pixel XL, and supported Nexus devices, indicating that compatible products are to start receiving the update shortly, presumably no later than tomorrow. Signed factory images and full OTA files for Google's devices are available for download by following the links below.
Apart from the 2016 Pixel flagships, owners of the Nexus 6P, Nexus 5X, Nexus 6, Nexus 9, and the Pixel C are all able to manually flash the update as of this writing, whereas images for the Nexus Player will presumably go live shortly. If you're seeking to flash the October Security Update to your Android device, note that Google's full OTA files listed below aren't identical to the ones you'd receive via an over-the-air upgrade and are much larger in size, though the end result of flashing either should be the same as far as your security patch level is concerned. The main advantage of flashing full OTA files over factory images is that you don't have to unlock your bootloader or manually wipe your partition, nor will the installation itself automatically delete any personal files you may have stored on your smartphone or tablet. As always, users seeking to flash the new update are advised to carefully follow Google's instructions or wait for the OTA update to arrive if they aren't confident in what they're doing so as to avoid any issues.
The full Security Bulletin for the latest update has yet to be publicized by Google, though its current listing indicates that flashing the update onto your device will bring its security patch level to the one dated October 5th. Following the rollout of the software package to members of the Nexus and Pixel product families, the same update should gradually make its way to third-party devices, with one exception being Nokia that may push it out by the end of the week for some of its models as it already has a (short) history of being swift to optimize Google's security patches for its offerings.