How tall is it? If it is tiny then it is likely to be Oxalis corniculata. If so then it is one of the most pernicious and wide spread of weeds in the world. It is now found on almost every continent. It is almost impossible to get rid of.
Anyway, the plant in the image is an Oxalis of some description.

that's what it looks like to me too. pretty but very invasive.

I agree it's Oxalis and it's a terrible weed and difficult to get rid of.

Been having a look around and I think it appears to be an Oxalis Plum Crazy.😀