Yammer is a social networking service that was launched in 2008 and acquired by Microsoft in 2012.
Basically, Yammer is a private network and is used for private communication between organizations or companies in predefined groups.
Ateeq Khan, a Pakistani-born researcher at The Vulnerability Laboratory Research, discovered multiple critical vulnerabilities in its software, as you can see in the video below:
An OAth bypass is capable of allowing remote attackers to bypass the protection card and impersonate the Auth account system in their web application.
For information, OAth is an emerging licensing model being adopted by a growing number of websites such as Twitter, Facebook, Google, Yahoo!, Netflix, Flickr, and many other providers and social networking sites.
As you can see in the video, the insecure implementation of OAuth in the Yammer network allows you to fish out users' emails, their conversations, and their profiles.
The vulnerability has of course already been patched by Microsoft.
