Three codes were hidden in the HTML source of the PRECURSORS RECEDING post on the Investigate Ingress blog.

[1] 6nsj4slmvhgbu6b4v

[2] arsgjarbofpherqohewugt

[3] t8cts9uomla7q9

Code #1

Observations

Passcode format is there, remember to apply the same logic to the keyword

Code #2

Observations

An old roman emperor will guide you

Code #3

Observations

14 characters with the right amount of numbers for a valid passcode