Back in July, 2015 I reported that the State Bar of California Standing Committee on Professional Responsibility had issued an "interim" opinion on confidentiality and was seeking comments on it before making it official. The opinion addresses the question of whether an attorney has a duty to keep confidential information that is publicly available.
As I reported back then, the general principle has always been that there is a difference between information that is publicly available and information that is "generally known." If the information is generally known, then you can say there is nothing to protect - because the information is known already. But not all publicly available information is generally known.
These principles had always been generally accepted and understood until the Virginia Supreme Court decided Hunter v Virginia in 2013, a heavily criticized outlier case in which the court surprisingly held otherwise.
On that point, California's interim ethics opinion reaffirmed the old principle concluding that "[a] lawyer may not disclose his client’s secrets, which include not only confidential information communicated by the client to the lawyer, but also publicly available information that the lawyer obtained during or related to the professional relationship which the client has requested to be kept secret or the disclosure of which might be embarrassing or detrimental to the client."
More than a year later, the interim opinion has been officially published as Formal Opinion 2016-195 and it is available here.
Professor Lisa Needham has posted a good short comment on the opinion. [As a bonus, in the process she also criticizes Avvo's chief legal ethics officer, something I have done a number of times too.]