mob spawner can be found in survival

Hi!
Thank you for your report!
However, this issue is Working As Intended.

• Mob Spawners can spawn, for example in the Stronghold

Please note, that mechanics of the game may change between updates.
Things such as graphics, sounds, world creation, biomes, Redstone, villagers, and animals may not work the same in current versions.

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Was it like this when you found it? Can you send your world seed?