Johansson, 34, has been married twice before -- first to Ryan Reynolds before their divorce in 2010, and then to French journalist and advertising exec Romain Dauriac, with whom she shares a 5-year-old daughter, Rose. The couple later divorced in mid-2017 after separating a year earlier.
ET spoke with Johansson at the star-studded event, and she joked about her plans to use Jost to play a prank on her Avengers co-star, Paul Rudd, when he hosted the season finale.
"I've got connections. I'm gonna make sure that his time is really difficult, you guys," Johansson explained of her plan, which she seemingly didn't actually enact when Rudd took the stage on Saturday. "I'm gonna sabotage him. I'm gonna come in from the inside [so] he doesn't know what's coming."