A security feature bypass vulnerability exists when Lync for Mac 2011 fails to properly sanitize specially crafted messages. An attacker who successfully exploited this vulnerability could cause a targeted Lync for Mac 2011 user's system to browse to an attacker-specified website or automatically download file types on the operating system's safe file type list. For an attacker to exploit the vulnerability, a specially crafted message needs to be sent to a targeted user. The targeted user does not need to take any actions after receiving the message.