Apple ended official support for OS X 10.6 Snow Leopard almost two years ago, but that hasn't stopped the company from issuing a small update for the older system. The update addresses compatibility for the Mac App Store included in Snow Leopard.

From Apple:

  • Installs a renewed intermediate signing certificate required by the Mac App Store. The certificate ensures that you can continue to use the Mac App Store in Snow Leopard to purchase new apps and run any previously purchased apps that use receipt validation.
  • Includes improvements to Mac App Store alerts.

OS X 10.6 Snow Leopard was released in 2009. It focused primarily on under-the-hood improvements over OS X 10.5 Leopard. This latest Snow Leopard update weighs in at 3.5MB, and can be downloaded directly from Apple.

Source: Apple (1), (2)