What happened? The California Public Employees' Retirement System (CaIPERS), in a brochure sent to retirees announcing an upcoming election, exposed all or a portion of the recipient's Social Security number (SSN) on the address panel. The number did not contain hyphens.

How many people affected? Roughly 445,000 retirees.

What was the response? CaIPERS notified each victim in a letter. The agency is also reviewing its policies, initiating an employee awareness training course and investigating whether it can replace SSNs with some other unique identifier.

Details: The mistake happened because staff did not realize the address files contained SSNs.

Quote: "While it is unlikely that someone would recognize the series of numbers as being a Social Security number except you, we consider this a serious incident," the alert letter read.

Source: "Apology sent over CaIPERS privacy error," Aug. 22, Sacramento Bee.