What type of bug are you reporting? Client
What is the bug?
When the opponent has more than one of the same Pokemon on their team and one of their Pokemon's abilities is revealed, the client incorrectly assumes that all of the Pokemon of that species have that ability. This leads to the client showing the player using multiple of the same Pokemon the wrong ability when hovering over the Pokemon (this is a more minor effect, the correct ability is still shown to the player by hovering over the Pokemon in the switch buttons).
More notably, this bug directly impacts Gen 7 Pure Hackmons, where spam teams are a common archetype. Since Gen 7, Pokemon that have transformed will always know in between turns what ability the Pokemon they are transformed into has. However, with this bug the client shows the incorrect ability to the player on the transformed Pokemon, when it should always show the correct ability. This bug makes it harder for users playing against spam teams to use Imposter to scout opposing abilities, when on cartridge it should always be known exactly what ability the transformed Pokemon has.
Are you able to replicate it? If so, how?
Here is a replay showing the bug and associated screenshots showing the client bug: https://replay.pokemonshowdown.com/gen9anythinggoes-2170421098
Screenshots
What is the bug?
When the opponent has more than one of the same Pokemon on their team and one of their Pokemon's abilities is revealed, the client incorrectly assumes that all of the Pokemon of that species have that ability. This leads to the client showing the player using multiple of the same Pokemon the wrong ability when hovering over the Pokemon (this is a more minor effect, the correct ability is still shown to the player by hovering over the Pokemon in the switch buttons).
More notably, this bug directly impacts Gen 7 Pure Hackmons, where spam teams are a common archetype. Since Gen 7, Pokemon that have transformed will always know in between turns what ability the Pokemon they are transformed into has. However, with this bug the client shows the incorrect ability to the player on the transformed Pokemon, when it should always show the correct ability. This bug makes it harder for users playing against spam teams to use Imposter to scout opposing abilities, when on cartridge it should always be known exactly what ability the transformed Pokemon has.
Are you able to replicate it? If so, how?
Here is a replay showing the bug and associated screenshots showing the client bug: https://replay.pokemonshowdown.com/gen9anythinggoes-2170421098
Screenshots