We are aware of the recently discovered vulnerability in the Sparkle update framework, utilized by our Mac software. Our development teams are actively working towards a fix, and we hope to have an updated version of Camtasia for Mac as soon as we can.
As of March 8, 2016 we have released an update for Camtasia (Mac) that addresses the Sparkle MITM vulnerability (Camtasia for Mac version 2.10.5). You can download the update by opening Camtasia and going to the Camtasia menu and choosing "Check for Updates" as seen below.
Camtasia for Mac: