Hello again -
HP has posted a security bulletin for the Heartbleed issue - HPSBPI03031 rev.1 - HP Officejet Pro X Printers, Certain Officejet Pro Printers, Remote Disclosure of Information found here:
I recommend that you review the bulletin for your product as you have a Prox476 device. Updating firmware to the latest will apply all patches.
Thank you and good luck!