There are 2 security venerabilities discovered in Skype.
1: that will allow a arbitary code to be ecexuted on your PC (Security is a Windows only Risk)
Fix. update to the latest version of Skype.
How: On the skype main window, click on Help, then Click on Check for updates.
This will take you to Skype update page.
More info
here,
here and
here2: Heap overflow in networking routine, This affects all Versions of Skype on All operatings systems, More info
hereFix: As with above, download the latets update.
Alternativly, Go to the skyp download page
here