I'm sure it has happened to others. From the growth, it looks like the grafting host is a Euphorbia, but the pic/plant doesn't help with any clues. If you try pricking the bottom part with a pin & it exudes milky sap, you will at least know to which family it belongs.

It could keep growing & you probaly could propagate it. You will have to watch the health of your E. lactea. If it starts failing, the growth may be stealing energy (?) from it. Maybe time for observation & experimentation! =)

there is no milky sap, so it must not be a euphorbia

I read that Euphorbia neriifolia is the one usually used for this graft. They could have removed the shield of thorns (those spots). So no bleeding? Hmmm!

See link below showing these plants with grafts...and growths of grafting stock.

Here is a link that might be useful: E. lactea w E. nerriifolia

It's grafted onto Euphorbia neriifolia. Grafting doesn't work outside of the family. Cacti-cacti, Euphorb-Euphorb, Citrus-Citrus, stone fruit-stone fruit. Your new growth is neriifolia and it's guaranteed to be diverting energy. Wether or not it can spare the energy is a different question.

definately euphorbia, maybe i didnt cut the surface enough to make it bleed

Wait until it gets a little bigger. Then you can cut it off and root it. It will grow into a large tree. The same happened to me.

{{!gwi}}