Professional Responsibility students often have a hard time understanding that the duty of confidentiality includes a duty to keep confidential information that is publicly available. "If it is publicly available," they often wonder, "there is no confidentiality to protect." But 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 - the information is known already. But not all publicly available information is generally known.
These principles have always been generally accepted and understood until the Virginia Supreme Court decided Hunter v Virginia in 2013, in which the court surprisingly held otherwise. But this aspect of the decision has been heavily criticized and, to my knowledge, not followed anywhere else.
To that point, the California State Bar Standing Committee on Professional Responsibility has proposed a new ethics opinion reaffirming the old principle. The opinion concludes 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."
The opinion is available here. The California Bar is asking for comments on the proposed opinion
through August 27, 2015. I think this is the correct view of the issue and should be supported. To learn how to submit
comments go here.