Comment # 1 on bug 1229276 from Larry Rainey

I have extension pack installed on my Tumbleweed with no problems.

You do have to shut down VirtualBox and all guest to make VirtualBox see the
Extension Pack after it is installed.

Here is my install script for the extension pack

# cat bin/addvbext
echo update VirtualBox
VBOX_VERSION=`/usr/bin/VBoxManage --version | awk -F_ {'print $1'} | awk -Fr
{'print $1'}`
VBOX_EXT_VERSION=$VBOX_VERSION
# echo Virtualbox version installed is $VBOX_VERSION and $VBOX_EXT_VERSION
VBOX_EXT=`echo
Oracle_VM_VirtualBox_Extension_Pack-${VBOX_EXT_VERSION}.vbox-extpack`
# echo File is $VBOX_EXT
cd /tmp
/usr/bin/wget http://download.virtualbox.org/virtualbox/$VBOX_VERSION/$VBOX_EXT
echo y | /usr/bin/VBoxManage extpack install --replace $VBOX_EXT
rm -f $VBOX_EXT

Here is proof that it is installed
https://paste.opensuse.org/pastes/d1c92d51af29