Is this what you have in mind?

```sql
        WITH sums as (
          SELECT
            signature,
            sum(high_count) as high_count,
            sum(medium_count) as medium_count,
            sum(null_count) as null_count,
            sum(none_count) as none_count,
            sum(high_count) + sum(medium_count) as med_or_high
          FROM exploitability_reports
          JOIN product_versions AS pv USING (product_version_id)
          WHERE report_date BETWEEN %s AND %s
            AND pv.product_name = 'Firefox'
          GROUP BY signature
        )
        SELECT
          signature,
          high_count,
          medium_count,
          null_count,
          none_count,
          med_or_high
        FROM sums
        WHERE
          high_count + medium_count + null_count + none_count > 4
        ORDER BY med_or_high DESC, signature ASC
```

That way we only get 1 signature PER REPORT but its data is limited by the date range in the parameters.