A new security patch update will soon be rolling out to Nexus devices and will be available for review for all other OEMs and carriers. This is the November security update for Android 6.x Marshmallow, and it fixes seven security vulnerabilities, two of which are considered critical.
Google indicated that OEM partners were of these security issues on October 5th. They also shared that source code patches are going to be released to AOSP over the next 48 hours. There have been no reports of anyone exploiting any of these security vulnerabilities, but/so it's great to see Google taking care of them so quickly.
Here's a link to the Google developer page for folks who want to download the Factory images: Factory Images for Nexus Devices
Of course, if you own a Nexus device, you should see an OTA rollout in just a few days if you would prefer to wait.