NR5103: Three UK Firmware - Security Question

Dear Zyxel,

i'm evaluating to buy an used Zyxel 5103E modem that have a THREE UK brand from an user of Aliexpress in China.

The product is perfect like new.

Firmware that i can see that is installed is : V1.00(ACBJ.0)b12 and is branded Three UK

My only complaint, as the product is used and is selled on Aliexpress and Ebay, if there is a method to verify and rest assured that the modem is not modded or that it don't contain exploit or other security problem inside it.

Or i can buy an used 5103E without any compliant?

Do you have a 5103E firmware public to download to reupload it into my modem when i will buy?

Thanks very much!

P.S: the firmware that is installed contain the fix about the security advisory CVE: CVE-2022-43389, CVE-2022-43390, CVE-2022-43391, CVE-2022-43392 ?

https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-command-injection-and-buffer-overflow-vulnerabilities-of-cpe-fiber-onts-and-wifi-extenders