A vulnerability in Skype that could expose members IP addresses may have been known to Skype officials as far back as November 2010. Microsoft bought Skype for $8.5 billion in October 2011. Security researchers in France and New York said today they alerted Skype to the same vulnerability in November 2010. Their research on the flaw was published the same month Microsoft purchased the company. Until the vulnerability is resolved, Skype users are urged to sign off when the service is not in use to minimize their risk exposure.
Source: https://threatpost.com/skype-ip-snooping-vulnerability-may-not-be-so-new-050112/76510/