What is this plant?
This looks like white avens, botanical name Geum canadense. It is a native that deer do not eat and thus is showing up more and more. It's a helpful groundcovering plant in wild or native areas, but in a manicured landscape it does tend to get around. It's not hard to pull from moist soil.
The interesting thing about this plant is how different the mature plant looks from the first year plants: https://www.wildflower.org/plants/result.php?id_plant=geca7