Thanks, Werner.

I belatedly note that for my Knoppix 7.4.2 that if I look at
Synaptic>properties>versions, there are other version choices
including the testing dfsg-3(testing) already available under
package>force version. Seems like that might be a viable
means of upgrade for Knoppixers as well. What do you think?

I have a similar but different situation with another Debian-derived LiveUSB,
with which you are familiar, that uses ntpdate without ntp, and for
which no version alternatives similar to Knoppix's show up in Synaptic.
I presume you would recommend your aptitude approach for that system's
security upgrade as well?

Also, a belated seasons greetings to you.