Players have found a way to exploit the matchmaking system in Warzone. Although skill based matchmaking doesn't currently exist in Warzone, a method of influencing the difficulty of a lobby was still discovered. The method was found by popular YouTuber "Rara" and involved a site called SBMM Warzone. SBMM Warzone is a site that allows players to search a username or lobby ID. When viewing a player's profile on this site, viewers can see what lobbies they've been in and what the stats are for the average player in the lobby.
Rara released a video about the site and the method that goes into more details and statistics on the site. Essentially, there is a way for players to join less skilled lobbies. In fact, the most difficult part of the method is that it requires at least two accounts. Rara specifically named content creator "Hydro" as guilty of using this method.
At the moment, it's unclear how to stop players from using this method. However, there are several instances of players being temporarily banned for tampering with an in game matchmaking system.