The Houston Astros were found to have been stealing signs electronically during their 2017 season (the year they won the World Series). A good breakdown of instances can be found here.
Baseball has a long and rich history of cheating, and this will no doubt go down as some of the most sophisticated to have been uncovered in the history of the sport. This particular instance seems to also fit in with a long history of poor corporate management of the league and a fanbase beholden to nostalgia and stubbornly opposed to any sort of change that might make the sport more resilient. Whatever.