I use Virtualbox at work on my LEAP 15, but at home i don’t need Virtualbox.
Every time i run system update, it install Virtualbox. I remove Virtualbox and next time i run system update, its back again.
I suggest that you uninstall it. And then lock it, so that it stays uninstalled.
To lock, you can use “zypper al” (and check the man pages). Or, I find it easier to use Yast Software Management. With Yast, right-click on package and select the option to lock it (or block or taboo – I think the name has changed recently, but you will recognize it).