Security updates are usually incorporated into later Software Updates

Security updates released for Mac OS X are usually incorporated into the next OS X Software Update.

Security updates may also be available for software released independently from OS X. Software Updates are packaged in a manner to keep systems secure. Security updates are only offered to systems that need the update, and not to later versions that have incorporated the Security Update. For more information, see the "Some, but not all, updates are displayed" section of this document.