Hi, these are green stink bugs. You can easily combat them by removing the affected leaves. I would check the rest of the plant to see if there are more, and if so, cut those off as well. If there are too many, you can wash the leaves with a soap mixture, or if they are outdoors and don’t have any flowers yet, use a water sprayer, but be careful not to damage the leaves.
But the easiest way is to search and destroy :)