What should you do if you receive a bug marked as a "duplicate"?

1. Confirm duplication: Compare the number and description of the new bug with the found duplicate. Ensure they describe the same issue in the same functionality/component.
2. Analyze the root cause (optional): If the duplicate bug is already closed, check if the root cause and proposed solution are described. If the new bug contains additional information that may help in finding the root cause, add it as a comment to the duplicate.
3. Add a comment: Leave a comment on the new bug, indicating the number of the duplicate bug and briefly confirming that it is the same defect.
4. Change the status: Set the status of the new bug to "Duplicate" (or the appropriate status in the used bug tracking system).
5. Close the bug: Close the new bug with a note "Duplicate," referencing the main bug.
6. Notify the responsible person: If necessary, notify the person responsible for the product or functionality about the new duplicate, especially if the main bug is still open or the status has changed.

Important: If there is doubt whether the bug is a duplicate, it is better to discuss it with colleagues or a lead before closing.