Are there green balls on the bottom? Phyllanthus.

Whatever it is, it's multiplying because it's been allowed to produce and drop seeds in previous years. Mow/pull to break the cycle.

I agree with purple...chamberbitter. Horrid plant!

Do the leaflets fold up when stressed?

I think I have the same thing. Don't know where it came from.

Somehow I knew this was what it would be when I saw the title. I agree with chamberbitter and that it is a horrible weed.

I don't often call plants "horrible", but this one earns the name. If you saw one in somebody's landscape last year, there might be dozens or hundreds there this year. It is extremely prolific. If you check the BONAP map for Phyllanthus urinaria, this non-native is not supposed to be in my county. But it is here, and I'm seeing it rapidly spreading - usually in landscapes, but also roadside. And it isn't even discretely small, sometimes growing to about 2 feet tall.

Here is a link that might be useful: {{gwi:332054}}