Well it is - and as always with every extention: U can always go through the source code. Tip: Search all files containing http <--- as if the ext sends any of your data it will be to an url.
I have checked every extensions source that I've DL'ed either from Addons here or from Chrome. Only few has had tracking.
For extension proofing I'll recommend this: https://addons.opera.com/en/extensions/details/extension-source-viewer/?display=en
(if you use that then u don't need that other chrome install ext)
