A security feature bypass vulnerability exists when Skype for Business or Lync do not properly parse UNC path links shared via messages. An attacker who successfully exploited the vulnerability could execute arbitrary commands in the context of the logged-in user. The security feature bypass by itself does not allow arbitrary code execution. Instead, an attacker would have to convince users to click a link to a file.
In a file-sharing attack scenario, an attacker could provide a specially-crafted file designed to exploit the vulnerability, and then convince a user to click the link to the file.
The update addresses the vulnerability by correcting how Skype for Business and Lync handle links to UNC paths.