In brief: What do Amazon, Apple, Google, and now Facebook have in common? Apart from being the four most prominent tech companies, they've all been caught allowing workers to listen to users' audio recordings.

Bloomberg reports that Facebook has been hiring third-party outside contractors to transcribe audio clips from the Messenger app. The voice-to-text feature, which lets people speak their messages rather than type them, has been around since 2015, though users must opt-in to use it.

Workers listened to the audio clips to gauge the accuracy of the transcription tool, but Facebook didn't make this very clear. "Voice to Text uses machine learning. The more you use this feature, the more Voice to Text can help you," explains the support page.

Bloomberg writes that the contractors were not told where the audio was recorded or how it was obtained. They added that some of the conversations contained vulgar content.

Facebook confirmed it had been transcribing users' audio but said it has now stopped the practice. "Much like Apple and Google, we paused human review of audio more than a week ago," the company said Tuesday.

Back in April, it was reported that thousands of Amazon workers and contractors from around the world were listening to voice recording captured by Echo devices---a means of improving Alexa performance. It was later reported that Google was doing the same thing with its digital assistant, though it paused the practice after voice clips were leaked. Even Apple, which prides itself on protecting the privacy of its users, had contractors listening to Siri recordings. The iPhone maker later said it was suspending Siri grading while it conducted a "thorough review."

While it may have stopped the practice, the news will come as another PR blow to Facebook. At least it's not as bad as the long-running rumor that it secretly records user conversations for targeted advertising, something Mark Zuckerberg had to assure congress wasn't true.