What is the confidentiality requirement for unpublished patent applications?

Unpublished patent applications are subject to confidentiality requirements under 35 U.S.C. 122(a). MPEP 405 addresses this in the context of interviews:

However, an interview concerning an application that has not been published under 35 U.S.C. 122(b) with an attorney or agent not of record who obtains authorization through use of the interview request form will be conducted based on the information and files supplied by the attorney or agent in view of the confidentiality requirements of 35 U.S.C. 122(a).

This means that for unpublished applications, the USPTO will only discuss information provided by the authorized attorney or agent to maintain confidentiality.