It pushes the firmware file farad_base_pp1_FDP1CN1416AR_nbx_signed.ful by netcat (nc.exe) directly to the printer port 9100.
(Windows only:) Run the BAT file (on recent Windows perhaps needed to right-click and Run as administrator.Edit in NOTEPAD or other editor the BAT file 8610_FW_1416_DOWN.BAT to reflect the real IP address of the printer.You need to whitelist nc.exe in your antivirus/anti-malware in order to proceed, or download another version of netcat/ ncat that the AV software accepts.) Download the firmware, netcat and the batch file with the template of the command ( Warning, many Windows antivirus software consider netcat as malware, hacktool because it indeed often is used as part of malware.Find the IP address your printer is connected to (Ethernet or wireless, disconnect printer from USB if you had it connected that way).
Some Brazilian folks posted a video on Youtube with a guide how to downgrade the firmware, and most important, published a link with the particular firmware version that makes the printer recognize the cartridges as valid! This is an English version of the manual how to do it:
For HP OfficeJet Pro 8610, some automatic firmware upgrade caused that many older and non-original or refilled cartridges stopped working, being marked as damaged. Even though US Magnuson-Moss Warranty Act and European rules on fair competition make it clear that printer manufacturers must not block using non-original inks and toners, and even warranty must not be void just by the mere fact of using non-original material, It’s becoming increasingly difficult to use alternative print material. Printer manufacturers really want you to buy their genuine, overprices ink cartridges and toners. The following article is kept for reference as it was the only way how to solve the issue with non-working OfficeJet printers for about one month after the blocking mechanism previously built to HP firmwares was triggered by the right date. Direct link to official 8610 firmware is here. For more information and link to official firmware fix click here.
UPDATE : HP finally surrendered after massive complaints of customers and released official firmware updates disabling the blocking mechanism for older and non-genuine cartridges.