Characters capes appearing on other characters elytra

On multiplayer and realms characters capes are appearing on other players elytra. Example- I have the creeper cape, my friend has pancake cape, and my other friend has no cape. When I put my elytra on it switches my cape to the pancake cape, and my friend without a cape also gets it. When my friend with the pancake cape puts on his elytra, he gets the creeper cape.