Facebook has fixed a critical flaw in its Facebook Messenger messaging app for Android that allowed callers to listen in on other users' surroundings without permission, before the called party accepts the call !!.
Facebook Messenger for Android has been installed on more than 1 billion Android devices, according to official Play Store page of the application.
Attackers could have exploited this flaw by sending a special type of message known as SdpUpdate, which would cause the connection of the call to the called party's device before it is answered.
Such as explains Natalie Silvanovich, a researcher at Google's Project Zero program “If this message is sent to the called user's device, it will cause the transmission to begin sound immediately while she is still ringing, which could allow an attacker to monitor the caller's environment."
Normally, the recipient of the call does not transmit audio until it agrees to accept the call, which is implemented when it clicks the accept button. Now if all this time someone was calling you a little more persistently than normal, you should probably suspect it. Especially if it was your other half.
Silvanovich found the issue in version 284.0.0.16.119 of Facebook Messenger for Android last month. To exploit this issue, an attacker would need to already have the rights to invite this particular person by bypassing certain eligibility checks (eg, being Facebook friends). It should also know how to use tools reverse-engineered its own Messenger app to force it to send a custom message.
The Facebook awarded to Silvanovich a $ 60.000 donation to find and reveal this Messenger bug for Android.
This year alone, Facebook reports that more than 1,98 millions dollars were given to researchers by more than 50 countries which reported over 1.000 vulnerabilities.