Apple's FaceTime has a major bug that lets others listen in on you before you answer the call (AAPL)

A major privacy flaw in Apple's FaceTime video chat product has been discovered allowing someone to secretly eavesdrop on another user before they answer the call, on both iPhone and Mac.

The bug is serious problem in one of Apple's flagship products, and is especially embarrassing given Apple's recent campaign touting its privacy bona fides compared to rivals like Google. It also comes less than 24 hours before Apple is due to report close-watched quarterly earnings in which the company is expected to report a decline in iPhone sales.

News of the privacy bug was making the rounds on Twitter on Monday and was picked up by blogs like 9to5Mac. Some users were urging iPhone owners to switch off FaceTime until Apple fixes the vulnerability.

Business Insider was able to replicate the privacy vulnerability in its own testing on Monday.

The bug in FaceTime allows someone to dial one of their contacts and listen in to the recipient's microphone before they actually answer the call. This can be accomplished by using the "add a person" feature after dialing the contact, and then adding your own number as the other person.

Apple did not immediately return a request for comment.

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