I have a volunteer plant that popped up in one of the empty pots on my balcony. It's growing well and I don't mind it being there, but I'm not sure what it is and would like to make sure it's not something that could overtake my other plants. Anyone happen to know what it might be? Thanks in advance for your help!

I pretty sure it is this
Acalypha australis is a herbaceous annual plant, growing 20–50 centimetres tall. Its leaves are oblong to lanceolate, 3–9 cm long, 1–5 cm wide and borne on petioles 2–6 cm long. The flowers are borne in axillary panicles, forming inflorescences 15–50 mm long.