The Pokémon Sword and Shield community is issuing a public service announcement for anyone playing the game right now: Be careful while using the game’s online features, as a new hack can cause crashes, and worse, affect your general online connectivity.

Surprise Trade is a multiplayer Sword and Shield feature that allows trainers to pick a monster and trade it for a random Pokémon from another player. Recently, however, reports are trickling out that some fans get an error when they attempt to complete a Surprise Trade, as you can see in the footage below:

POC for the Surprise trade Crash! pic.twitter.com/o6CtylL0mo — thecommondude (@architdate) February 12, 2020

Further, and more troubling, is that the crash is followed by general online issues once you reload the game — Pokémon Sword and Shield will reportedly crash whenever you try to use the multiplayer via Y-Com, as some fans are reporting on social media.

Credit to @architdate and @Sibuna_Switch for originally discovering this independently and confirming the behavior, and elevating it to TPCi prior to someone acting maliciously. It's recommended to not use Surprise Trade until a patch is released! — Kurt (@Kaphotics) February 12, 2020

According to Pokémon modder architdate, the issue is caused by the creation of malicious Pokémon that have been generated by hackers via specialized programs that can inject monsters into Nintendo Switch systems running custom firmware. These hacked monsters cause Pokémon Sword and Shield to play the trade animation over and over again until the game crashes. Right now, the wider Pokémon hacking community estimates that about 60 players have been affected at minimum, but the number may increase depending on whether or not knowledge of how to create the malicious Pokémon spreads, or if the parties involved continue to generate more creatures.

The Pokémon hacking community is a varied one, with most devoting themselves to only generate “good” monsters that are possible within the confines of the game. Actually, some hackers say they’ve already reported the issue directly to Game Freak and are awaiting a fix. The wider Pokemon community, meanwhile, is advising others to stay away from Surprise Trades until a patch is issued. The number of currently-affected users may be small when taking into account the millions of people who own Sword and Shield, but the resulting issue is severe enough that everyone should be careful, lest bad luck strike.

Reached for comment, Nintendo did not respond in time for press.