GraphQL Debug Mode is a feature that, when enabled, provides detailed error messages, stack traces, and additional debugging information in responses. While this is invaluable during development, leaving it enabled in a production environment can potentially expose sensitive information about the server's internal structure and implementation details.

In Django Graphene, debug mode is typically controlled by the Django `DEBUG` setting and the inclusion of `DjangoDebugMiddleware` in the Graphene configuration.

When debug mode is enabled, error responses may include:
- Detailed stack traces
- Database query information (including SQL queries)
- Internal server paths and file names
- Sensitive configuration details

Example of a response with debug mode enabled in Django Graphene:

```json
{
  "errors": [
    {
      "message": "Cannot query field \"nonexistentField\" on type \"Query\".",
      "locations": [
        {
          "line": 3,
          "column": 3
        }
      ],
      "path": ["nonexistentField"]
    }
  ],
  "data": null,
  "extensions": {
    "debug": {
      "sql": [
        {
          "sql": "SELECT \"auth_user\".\"id\", \"auth_user\".\"password\", \"auth_user\".\"last_login\", \"auth_user\".\"is_superuser\", \"auth_user\".\"username\", \"auth_user\".\"first_name\", \"auth_user\".\"last_name\", \"auth_user\".\"email\", \"auth_user\".\"is_staff\", \"auth_user\".\"is_active\", \"auth_user\".\"date_joined\" FROM \"auth_user\" WHERE \"auth_user\".\"id\" = %s LIMIT 21",
          "time": "0.000",
          "params": ["1"]
        }
      ],
      "python_version": "3.8.5",
      "django_version": "3.1.3",
      "graphene_version": "2.1.8",
      "graphql_version": "3.0.0"
    }
  }
}
```

Security Impact of GraphQL Debug Mode:
- **Information Disclosure**: Debug information can reveal internal details about the GraphQL server's structure, dependencies, and potential vulnerabilities, which could be leveraged by attackers to plan more targeted attacks.
- **Sensitive Data Exposure**: Stack traces, error messages, and especially SQL queries might inadvertently include sensitive information such as database structure, internal file paths, or environment variables.
- **Easier Exploitation**: Detailed error messages and SQL queries can assist attackers in refining their attacks by providing immediate feedback on what worked or didn't work in their malicious queries.
- **Performance Information Leakage**: The timing information provided for SQL queries could be used by attackers to infer the structure of the database or to perform timing attacks.