Researchers at Columbia University were able to hack an official HP management tool to include malicious programming in with a regular print job. It allowed the researchers to grab confidential information and even caused printers to overheat. Worse yet was that the hackers left no outward indication of the changed status on the printer software, leaving owners unaware of a security breach. The reprograming hack job lasted just 30 seconds.
HP was made aware of the flaw prior to the researchers going public with their findings.