You can start here: https://hackaday.io/project/176931-hp-printer-cartridge-control-module/details
HP printers are conceptually quite simple devices, the printer just moves the cartridge and the paper. The cartridge does all the actual printing. So you reverse engineer the pinout on the cartridge and you can make your 3d printer do normal printing. That's also how those little handheld cube printers work.
Seems it's exploiting vulnerabilities in some software called "Ivanti Connect Secure VPN", so unless you're running that, you're safe I guess. Says in the past they used vulnerabilities in "Qlik Sense" and Adobe "Magento". Never heard of any of those, but I guess maybe some businesses use them?