Automatic weights not working well I'm new to blender and following a tutorial. I finished rigging and set parent with automatic weights but for some reason it doesn't work well for me - the side of the body of the mesh moves when I move the IK_Hand in pose mode.
In the tutorial it moves good and only the hand and its relevant parts are moving.

Can you help me with this?

This is my file: Mushroom

Thank you!
Your normals are flipped, you can see it if you enable Face Orientation in the Viewport Overlays options, it messes up the parentage. Go in Edit mode, select all and Mesh > Normals > Recalculate Outside, or ShiftN. Then reparent With Automatic Weight.