A key paper on its safety from 2000 was retracted: https://news.ycombinator.com/item?id=46161125
Like the tobacco industry before them, a Monsanto employee proposed producing a scientific paper with outside scientists: “by us doing the writing and they would just edit & sign their names so to speak” — see https://retractionwatch.com/2025/12/04/glyphosate-safety-art...
There isn't one single study that glyphosate safety is based on. It's an intensively studied substance.