The skybox renders when the player is in certain reduced fog situations, leading them to be able to see the sun and sunset background in the overworld, and making the entire sky to be visible in the end, when it shouldn't be the case. These situations include:

1. When the player is below the lower height limit, in the void.
2. When the player is affected by the blindness effect.
3. When the player is affected by the powder snow / lava fog.

Other slightly different situations:

1. During the ender dragon fight (probably intended).
2. When the player is underwater at low render distance (MC-126772 / MC-152504).

Expected result

In all of these situations, the player shouldn't be able to see the skybox because the fog would be able to hide it.

How to reproduce

1. Load a world, set the time to around 12500.
2. Give you blindness with the /effect command.
3. The skybox is visible.