Viber vulnerability, allowing to listen to someone else's conversation

I came across the opportunity to listen to other people's conversations in Viber by chance at the beginning of October 2016. Vulnerability seemed to me not too pleasant, so I contacted customer support and described the algorithm to reproduce the non-standard behavior of the messenger.

I am writing this publication in the hope of attracting the attention of Habrasoobshchestvo and its wider publicity in the hope that it will encourage developers to fix this annoying bug, since communication via email with Viber support did not bring any results.


Initial data
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Two subscribers are talking to each other through Viber, let's call them A and B. During the call, subscriber A receives a call, but not through Viber, but through a mobile network. Subscriber A answers the call, thus subscriber B is on hold.

How to overhear a caller A conversation

Subscriber B, while on hold, presses the “Hold” button twice, thereby putting and removing the hold mode on its part, this option is available when talking on a mobile phone or tablet, I did not find such a button in a stationary client.

Having done these actions, subscriber B hears the conversation of subscriber A, but without the opportunity to participate in it. Subscriber A does not understand at all that at this moment he is already “overheard” and when he finishes talking on the mobile network he returns to Viber to continue the dialogue with the subscriber B.

This problem is reproduced on Android, I do not have the opportunity to check on iOS.

This issue was sent in support of Viber on October 4, 2016 and received the number # 2620428. On November 22, I reminded them that 2 Viber updates had already been made since I sent the first letter, but the problem persists.

The answer to the second letter was received only on November 28:

We sincerely regret that you encountered this problem when using Viber. At the moment we are continuing to work on investigating this issue. As soon as the results are obtained, we will definitely inform you about it. Thank you for your patience.

Best Regards,
Trinity L.
Viber support team
Quick question? Tweet to @ViberHelp

To date, the problem remained in its place. I hope that this post will help find the strength and means to eliminate this bug.

While writing an article, the problem was corrected in the update that came on the phone yesterday, but it may still be relevant for those who did not update.

UPD: from the messages in the comments, it became clear that the problem has not yet been fixed for iOS and BlackBerry .