The HP LaserJet M209dw ($149) is essentially the same printer as the HP LaserJet M209d, but with a small bump up in price and the addition of Wi-Fi support (denoted by the "w" in the name).
The researchers claim that the vast majority of printers from HP’s LaserJet line accept firmware ... stating that all models built in 2009 and beyond require firmware to be digitally signed.