problem: there is no update button in the webui, and there is no usb storage feature. you also do not want to install the latest firmware, for obvious reasons.

• enable firmware signature checking on your printer, just in case
• download the latest firmware updater for your printer
• find the firmware version you want (good luck, also dont make sure it won't enable dynamic security)
• open the new firmware updater in CFF Explorer and replace the resource called FILE

• "save as", run the updater, click update and pray. tested with network printing but it should work with USB print too

note: if you break your printer i take absolutely zero responsibility, buy yourself a brother printer next time