A spoofing vulnerability exists when a Lync Server or Skype for Business Server does not properly sanitize a specially crafted request. An authenticated attacker could exploit the vulnerability by sending a specially crafted request to an affected server. The attacker who successfully exploited this vulnerability could then perform cross-site scripting attacks on affected systems and run script in the security context of the current user.
For the vulnerability to be exploited, a user must click a specially crafted URL that takes the user to a targeted Lync or Skype for Business site.
In an email attack scenario, an attacker could exploit the vulnerability by sending an email message containing the specially crafted URL to the user of the targeted Lync or Skype for Business site and convincing the user to click the specially crafted URL.
The security update addresses the vulnerability by helping to ensure that Lync Server and Skype for Business Server properly sanitize web requests.