http://download.wdc.com/nas/sq-030401-230-20140415.deb.zip
Either just wget/unzip from the disc or download it, unzip it and copy to the disc.
BUT… I don’t take any responsability. Disclaimmer, blah, blah:
You’d have to edit the file /usr/local/sbin/updateFirmwareFromFile.sh commenting out the lines 256 through 259 since it won’t allow you to apply any version lower than the existing one:
# if [-z "${update_container}"] && ["${vnew}" -lt "${vnow}"]; then
# error="failed 200 \"invalid firmware package\""
# pre-update_error $error
# fi
After that, you can downgrade the disc:
/usr/local/sbin/updateFirmwareFromFile.sh /DataVolume/shares/Public/sq-030401-230-20140415.deb