Comment 4 for bug 1330480

If someone wants to try this patch to see if it fixes your issue, you need to do roughly this:

mkdir ~/src/dunst_apt ; cd ~/src/dunst_apt
sudo apt-get source dunst
cd dunst-1.0.0/
sudo apt-get build-dep dunst
# apply the patch, i.e. insert the call to g_variant_unref(content) at the right place in dbus.c
dpkg-source --commit
# enter some temp name for the patch like "fix-spotify-leak" or so
debuild -us -uc
cd ..
sudo dpkg -i dunst_1.0.0-2_amd64.deb

....or if you think that sounds too complicated, just download and "dpkg -i" the following pre-built .deb (suitable for 14.04 x64):
http://temp.minimum.se/dunst_1.0.0-2_amd64.deb