Since it is freshly dug and potted, I'll take a wild guess at a white flowered Campanula, species I could not find. That's mint behind it. Both are vigorous spreaders which is why they are common pass-a-long plants.

Added: Campanula punctata, Spotted Bellflower.

There are two different plants in the pot. Neither is Lapsana communis. One is mint. Do you have a picture of the other one in situ and in focus?

in the back is mint, the front plant someone sold me telling that it was Japanese's ester, does it look like Japanese's aster?