https://files.hddguru.com/download/Firmware%20updates/Toshiba/fw-disk-toshiba-MG08-S-4305.zip It is latest china firmware, it can be installed on oem drive. OEM firmware you can obtain from toshiba support

Trojan:Win32/Malgent!MSR
Detected by Microsoft Defender Antivirus

Aliases: No associated aliases
Summary

Trojan:Win32/Malgent!MSR is a malware strain used by Diamond Sleet, a North Korean state-sponsored threat actor, in its software hijacking campaigns. The malware is primarily delivered through social engineering attacks using WhatsApp, LinkedIn, OneDrive, and Google Drive, where victims receive *.zip files containing trojanized software. These zip files often use job-related lures, masquerading as legitimate engineering, maintenance technician, or program manager documents. Once the victim runs the software, DLL hijacking occurs, allowing the attacker to install a backdoor, enabling further payload execution and credential theft.

The easiest thing to do is to disable the driver digital signature check for the duration of the update.
Google will help you with how to do this in your system.
And I don't know if this ancient thing will work in Windows > 10.

don't know if this is any help: https://forums.servethehome.com/index.php?threads/toshiba-mg09-how-to-upgrade-the-firmware.40130/page-2

mainly about openseachest, the syntax and directory permission stuff they mention

example MG08ACA16TE:
fw 0101 can be upgraded directly
fw 0102 cannot be upgraded directly

(1) Fixed the issue where drive incorrectly reported delay errors as BCRC errors.
(2) Fixed the issue where the write command was executed twice internally, causing a BCRC error or SATA I/F protocol error.
(3) Fixed an issue where host commands could cause an abort error if there was a conflict between background processing and host command processing
(4) Fixed the issue where the standby or sleep command could cause the drive to hang in certain rare circumstances.
(5) Fixed the data comparison error problem caused by the power failure protection failure of the Flush Cache command writing data after the power is turned off.
(6) Fixed a data comparison error with incorrect cache registration information that occurred during retry during pre-reading
(7) Fixed a data comparison error when power is turned off because the Flushcache command returns a response without data protection
(8) Fixed a problem that caused the drive to hang at certain times and in rare command modes
(9) Fixed the issue where the RESET command hangs after the Standby command, which includes multiple retries to flush cache data to the Media Cache.
(10) Fixed the issue where when the SCT timer is limited to less than or equal to 1 second, an SCT timeout occurs after a cache refresh command within 1 second, causing a protocol error.
(11) Fixed the issue where the data could not be transferred when the read data was found in the cache data.
(12) Fixed motor driver settings for counter recovery timeout from Idle-C state
(13) Fixed the initialization sequence in the boot sequence
(14) Changes to avoid registering CRC errors in the SMART error log
(15) Fixed the long command delay issue when deep read retry occurred
(16) Improved the latency of read verification commands

(1) Changing the Patrol Seek conditions to improve low IO performance
(2) Changed the process of searching for tracks without LBA assignment during ATI (adjacent track interference) scan
(3) Changed to use Flush Cache command to save ATI management information
(4) Disable the learning function that activates the vibration mode selection during the ATI refresh sequence
(5) Improved read retry handling during ATI refresh
(6) Added more checks to prevent the HDD from referencing the wrong current servo frame number.
(7) Improved ATI count when writing 2 tracks

Hi, I came across this thread with similar questions. I'll be using the disk standalone or in Linux software RAID. Maybe the fixed edge-cases won't hit me?
Finally there's a thread over at Computerbase from 2 years ago, user has the 0103 firmware with TOSHIBA MG08ACA16TE but was missing the update tool