There are various firmware versions available for the ZTE F601, and some of them have been patched to fix known issues. However, I couldn't find a specific, widely available patched firmware for download.
If you have obtained a verified, clean firmware file (directly from a hardware supplier, not a random forum), here is the standard upgrade path: zte f601 firmware download patched
The ZTE F601 is a classic GPON ONT (Optical Network Terminal). It’s widely used by ISPs (Internet Service Providers) worldwide, from Telefónica in Spain to Bell in Canada, and countless carriers in between. There are various firmware versions available for the