[kubuntu] Tails guest needing guest additions? (Kubuntu host)

I just upgraded from Tails 0.17 to 0.17.2. However now when I boot from the iso in VirtualBox, the mouse is jumpy and sometimes vanishes, and simply acts strangly. This same thing happens with Kubuntu, Fedora, and Debian when they're installed through VirtualBox without guest additions installed. But why should the update from 0.17 to 0.17.2 suddenly require (I presume) the guest additions?

How do I prevent the jumpy cursor when running Tails 0.17.2 in a Kubuntu host?