The bug

The "Bring Home the Beacon" advancement is granted when a player gets near a beacon, even if it was not built by the player, under certain circumstances. This closely relates to MC-117636.

How to reproduce

• Create a new creative world, or revoke the advancement by typing /advancement revoke @s only minecraft:nether/create_beacon.
• Assure you are not in Spectator mode.
• Teleport to the roof of the nether by typing the command /execute in minecraft:the_nether run tp 0 128 0.
• Run the following commands:

1. /fill 3 130 4 1 130 6 iron_block replace
2. /setblock 1 130 13 iron_block
3. /tp 1 131 13
4. /setblock 2 131 5 beacon

• Wait for the beacon to activate.

Observed result

You get the advancement even if you did not build or place the beacon.

Expected result

You wouldn't get the advancement, since you did not build or place the beacon.