If you create a map of the End and then frame it in the Overworld (or vice versa), a green marker appears at the coordinates of the item frame, even though the item frame is in a different dimension from the one being shown on the map. The attached image shows a map of the End in an item frame in the Overworld, with the green marker showing up at a location that's never even been visited in the End dimension, let alone having a framed map there.

Steps to reproduce

• Create a superflat with the void preset and create a map and upgrade it to level 4 (this is to better observe the bug)
• Run the following command:

  /execute in minecraft:the_end run teleport @p ~ 100 500

• Use setblock to place a block at the coordinates and place the map in a item frame at that location

  /setblock ~ ~ ~ stone

• Observe that the green marker will appear even though it's in the wrong dimension and that the marker is in unexplored territory.