Google has sent a security patch as an update for its all Nexus users. Over 1 billion devices are protected via Google Play, which conducts hundreds of millions of antivirus-like security scans of devices per day seamlessly in the background.
Android is open source so that anyone can comb through the code to identify & address potential security risks, which makes the platform stronger. Android Security Rewards Program financially rewards security researchers who invest their time and their effort in helping make Android more secure.
For the past 3 years, google have been notifying Android manufacturers every month through bulletins of security issues so that they can keep their users secure.
Nexus devices have always been among the first Android devices to receive platform and the security updates. Nexus devices will receive regular OTA updates each month focused on security, in addition to the usual platform updates.
The first security update of this kind began rolling out today, Wednesday August 5th, to Nexus 4, Nexus 5, Nexus 6, Nexus 7, Nexus 9, Nexus 10, and Nexus Player.
Nexus devices will continue to receive major updates for at least two years & security patches for the longer of 3 years from initial availability or 18 months from last sale of the device via the Google Store.
Source: Google [source]