Apple today confirmed that it has closed what it described as "a security hole" in the iTunes Music Store that allowed users to purchase songs without digital rights management technology (DRM) attached.

As a result, users of iTunes versions earlier than 4.7 will need to upgrade in order to continue purchasing songs. This update also locks out users of PyMusique, a software application for Windows and Linux that served as an alternate interface to the iTunes Music Store.

Developed by several programmers, including Jon Lech Johansen, aka "DVD Jon," PyMusique allowed users to preview songs, register for an iTunes Music Store account, buy songs and re-download them after purchase – a feature that iTunes does not support.

Most notably, however, songs purchased and downloaded using PyMusique are not encrypted with FairPlay, the DRM technology used for all songs downloaded from the iTunes Music Store using iTunes itself.

"The security hole in the iTunes Music Store which was recently exploited has been closed, and as a consequence the iTunes Music Store will now sell music only to customers using iTunes version 4.7," an Apple statement said. "Customers using an older version of iTunes (only around 15 percent) will need to get the free upgrade to iTunes 4.7 to continue purchasing."