On Thursday, Apple allowed CNBC into its top-secret testing facility to show how it tests the iPhone 6.

Apple is scrambling to play down concerns over reports that the iPhone 6 is prone to bending if left in a pocket during the day. CNBC was allowed to film a brief clip inside Apple's testing facility that showed the kind of rigorous tests that Apple puts its new devices through:

A computer monitor in the iPhone testing facility was seen to be running Windows XP. Although it looks embarrassing, it's actually common for manufacturing facilities to run Windows. Beta News spotted that Microsoft's 13-year-old operating system is used by Apple to test new iPhones.

Microsoft stopped supporting Windows XP back in April, but thousands of businesses around the world are still using it for their computers. It seems that Apple is one of them.

This isn't the first time that Apple has been caught using Windows to help make its products. A tweet sent by Apple CEO Tim Cook in June accidentally revealed a computer running Windows in the company's factory in the US.

Tim Cook/Twitter