Ang Cui presents Print Me If You Dare at Chaos Communications Congress (28C3) in which he explained how he reverse-engineered the firmware-update process for HPs hundreds of millions of printers. In Andrei Costin’s presentation “Hacking MFPs” he covered the history of printer and copier hacks from the 1960s to today. Cui’s technique for infecting printers involves the more limited Printer Job Language, rather than PostScript, and injects code into processes running on the printer.
Source: https://thehackernews.com/2012/01/print-of-one-malicious-document-can.html