The security patch level is July 5th, and though it seems to be three days into the future, Google's security patch level is usually on the 5th.
Google notes that there are no reports of customers being affected by these security issues. The update also addresses security issues that affect various Qualcomm components. This 290.2MB update includes the July security patches, similar Android Auto fixes, and the "latest Google Android P code integration".
The Android Developer Preview is available for Pixel and Pixel 2 phones, once enrolled in the Developer Preview Beta Channel which you can do by going here. That said, it times well with the release of the latest security and bug patches, including a functional improvement to the Pixel 2 and Pixel 2 XL on Wi-Fi router latching. The updates are already pushing out as Over The Air updates to phones now - or you can download the OTA or Full images of Android P DP4 from the Android P dev site. The OTA Zip files can be sideloaded on top of the existing software.
Google has launched the monthly security update for all of its now supported devices. You are recommended to back up your data before beginning the installation process.