In an extensive blog post. on the game's many recent problems, Fiedler criticised Ubisoft for developing the game with what looks like a trusted client network model. Simply put, it trusts the job of tracking key gameplay information to individual players, rather than the server.
This information can include a player's position in the game, how powerful they are, or what abilities they have - such as being able to walk through walls.
On PC at least, copies of the game can be hacked to edit this data, giving users an unbeatable advantage.
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As for console versions, the outlook is a little brighter, but only with a lot of work:
"[Ubisoft would need to] fix all lag switch timing exploits and disable players moving and shooting while lag switch usage is detected."