On very old models (DocuPrint, N-Series), there is a physical jumper on the main circuit board labeled "NVRAM Reset" or "Password Clear." This requires opening the device, which voids warranties. Do not attempt unless you are a certified tech.
Before you search for a downloaded tool, try the legal backdoor. Most Xerox printers have a web server built-in. xerox admin password reset tool download
The exact steps depend on your model (e.g., WorkCentre 78xx, AltaLink B80xx, VersaLink). Always follow instructions provided by Xerox support. On very old models (DocuPrint, N-Series), there is