Apple Inc. (NASDAQ:AAPL) has finally released Snow Leopard to the wild to fend for itself.

When the Cupertino, Calif.-based company released a security update for its OS X operating system, it did not include a patch for version 10.6, better known as Snow Leopard. Apple did provide updates for the latest version, Mavericks (10.9) as well as Mountain Lion (10.8) and Lion (10.7).

The 2009 version of Apple’s desktop and laptop operating system was very popular among users. Computer World estimated that 19 percent of Macs still run on Snow Leopard while only 16 percent run its successor, Lion.

This also means that nearly one out of five Mac computers are now vulnerable to 21 security weaknesses that Apple fixed with the latest update. This is especially troubling considering Apple doesn’t have an official policy for when it stops supporting operating systems and hasn’t let users know that their computers are now vulnerable.

Apple has made no official statement that it is ending support for Snow Leopard, like Microsoft did with Windows XP earlier this month, but this is pretty par for the course for Apple. Apple traditionally only provides updates for its newest operating system and its immediate predecessor, meaning Snow Leopard should have lost Apple’s care back when Mountain Lion shipped in 2012.

Instead, Apple has weaned Snow Leopard off its support by refusing to provide security updates. Apple didn’t provide a patch for Safari 5.1.10, the latest version of Apple’s browser supported by Snow Leopard, when it repaired Safari 6 and 7 in December.

No actual Snow Leopards were harmed in the making of this article.