In O365 package, the Skype client auto hides the "Currently presenting" bar. So, many a times, after a Skype call ends and the chat window is not closed, the screen sharing continues to run without the presenter being aware of this.
this is a security risk. The thin yellow border around the edges of the screen does not seem to be very distinct.
in older versions of client, this bar used to be pinned by default whereas in O365 it is auto hide by default.
Either the yellow border should have some flashing effect
The 'Currently Presenting' bar should be pinned by default to remind presenter that the screen is still being shared.