Certified GKH Gardening Expert
It looks more like Dame's Rocket. Did you plant seeds for that a year or two ago? It's biennial so wouldn't have produced flowers the first year. It also reseeds easily so if you have a neighbor who grows it, birds might have dropped seed.
It's a great butterfly nectar plant and it's a host plant for cabbage white butterflies. It can be invasive, however, you will see all the seeds it produces.