def lead_scorer(lead_data):
    """
    Scores a lead based on its likelihood to convert.

    Higher scores are given to github security issues and lower scores for inactive accounts.

    Args:
        lead_data (dict): A dictionary containing the lead's data.

    Returns:
        int: The score of the lead, ranging from 0-100.
    """
    if 'source' in lead_data and lead_data['source'] == 'github_security_issue':
        return 90
    elif 'activity' in lead_data and lead_data['activity'] == 'inactive_account':
        return 10
    else:
        return 50