White Currant. Ribes rubrum. It's just a colour variant of the same species as Red Currants. Gooseberries don't grow in bunches, are thorny and have grape size or larger fruit. Jostaberries are dark blue/black and the bunches are shorter and less full.

I don't remember ever buying a currant -- but I will enjoy it all the same! Very likely it was mislabeled.

Possibly mislabelled. Possibly just a hitchhiker. Currants root very easily. Even a bit of twig inadvertently dropped in a pot at a nursery could result in a plant.

I'll have to go out and take a closer look at the pot it is in; it would be interesting if it were a different plant in there originally.