In recent days, users of both Microsoft Teams and Google Hangouts have reported receiving apparent test notifications mentioning FCM through the app.
Users of Microsoft Teams recently took to social media to complain that they were getting mysterious notifications from the app with captions like “FCM Messages.” Microsoft said in response that it was aware of the problem, which appears to be linked to testing related to a recently disclosed issue with Google’s Firebase Cloud Messaging (FCM) cross platform notification tool.