What is the test for disqualification of an attorney who improperly obtained privileged information from an opposing attorney?

10 Cal.App.5th 1083, 1120 ["'[d]isqualification is proper as a prophylactic measure to prevent future prejudice to the opposing party from information the attorney should not have possessed'; an affirmative showing of existing injury from the misuse of privileged information is not required"]; see Clark v. Superior Court (2011) 196 Cal.App.4th 37, 43-44, 54-55 [attorney received opponent's privileged documents from his own client, who had stolen them when fired, rather than through inadvertent production by opposing party or its counsel; disqualification was proper prophylactic remedy based on evidence attorney had reviewed the documents more than minimally necessary to determine their privileged nature and had affirmatively used some of the substantive information in the privileged documents].)