SAN FRANCISCO — The iPhone as an eavesdropping device? Watch out. It can happen.

On Monday, Twitter and other social networking sites lit up with anxious Apple users after the news site 9to5Mac reported on a strange glitch in the company’s iPhones. The issue: It turns out that an iPhone user can call another iPhone user and listen in on that person’s conversations through the device’s microphone — even if the recipient does not answer the call.

The problem was the result of a bug and involves Apple’s FaceTime app for placing video and audio calls over an internet connection. The bug could also give a caller access to a live feed of the recipient’s camera.

On Monday night, Apple said it had disabled Group FaceTime, the feature that was causing the glitch.

The glitch is embarrassing for Apple, which is set to report disappointing financial earnings on Tuesday. The Silicon Valley company has long positioned itself as a protector of user privacy offering more secure devices than its rivals.