A recent beta update is rolled out to Normal Pixel XL Users by Mistake. Before any major update, a beta update is rolled out for the beta testers. They check the update after installing and reports back if any bug or issue persists. So that Google Solves it and then slowly rolls out the update via OTA to all the normal users. This decreases the chance of Bug in the final update, as it’s already been tested by the Beta Testers.
This was first found by Android Police that the OTA was a beta update & it came to a normal Pixel XL user. “Confidential Internal Only – This is a confidential Googler-only OTA to update your Pixel XL with May 2017 security patches. You may use your device normally but do not discuss or comment on this update externally. Send feedback to [email protected] See go/nougat for more info!”
The good thing is that the update was of only 62 MB. So it’s not a big update to make any phone unstable for daily use. It was rolled out to give monthly security patches to keep the phone safe.