A security hole was announced today in HP LaserJet printers allows attacker to make the printer smoke and shut down, erase the firmware, replace the firmware, and/or use the printer to steal sensitive data. The attack may also work on other manufacturers’ printers as well, but has not been tested.
Unfortunately there aren’t any good technical details in the article or methods of preventing the attack, other than protecting your printer from the Internet. If your printer is attacked it’s possible that there will be no way to fix the firmware. For now it’s a matter of waiting for HP to realize this is a problem and releasing a firmware update, and putting your printers behind a firewall.
http://www.infoworld.com/t/hacking/security-researchers-say-hp-printers-vulnerable-hackers-180253