When pureeing hot soup, an immersion blender is a handy tool. You can puree right in the pan with little or no extra mess.
Hot soup (or other hot liquids, for that matter) will steam and expand in the blender, which can push the top off and cause a mess and burn hazard.
When pureeing hot soup, do it in batches. Fill the blender 1/3 to 1/2 full, remove or loosen the center cap from the lid of the blender. Cover the lid with a folded dishcloth and hold it down when blending. Repeat with the remaining batches.