have you got a TA booking? whether it works or not would be interesting.

in any case, presumably you were already nervous since someone who could access your booking on MMB could already cancel it. so i am not sure why this raises new issues.

now, it may be that as a general point BA would be better off implementing 2FA to access bookings like QR does where you have to enter a 6 digit code sent to your phone to load up MMB.