The Packers apparently never stop tweaking their roster. In this case, it might have by necessity because they placed practice squad S Anthony Levine on the injured list. Packers.com announced they've signed former Nicholls State WR Antonio Robinson. Though they did take a look at signing former CB D.J. Clark, replace a defensive back with a defensive back, but they wanted Robinson instead.
He was released by the Bears back in August, but I doubt he's got any inside information. NFL Draft Scout has him at 6'1" with 4.50-4.56 speed in the 40. He's got the size and speed to make it in the NFL, but he's had trouble staying healthy. Maybe he was just signed now so they can take a closer look at him in a few months.