 
        When developing web applications, there are several key areas to focus on regarding cybersecurity:
def create_user
  username = params[:username]
  if username =~ /\A[a-zA-Z0-9_]+\z/
    # Valid username, proceed
  else
    render json: { error: "Invalid username" }, status: :unprocessable_entity
  end
end
begin
  # Some operation that might raise an exception
rescue StandardError => e
  Rails.logger.error("An error occurred: #{e.message}")
  render json: { error: "An unexpected error occurred" }, status: :internal_server_error
end
Configure CORS policies correctly to prevent unauthorized access
Implement security headers like Content Security Policy, X-Frame-Options, etc.
# In config/initializers/secure_headers.rb
SecureHeaders::Configuration.default do |config|
  config.x_frame_options = "DENY"
  config.x_content_type_options = "nosniff"
  config.x_xss_protection = "1; mode=block"
  config.content_security_policy = {
    default_src: %w('none'),
    script_src: %w('self' 'unsafe-inline'),
    connect_src: %w('self'),
    img_src: %w('self'),
    style_src: %w('self' 'unsafe-inline'),
    font_src: %w('self')
  }
end