[Canada]

Obviously the app maintainer could push an update that simply leaks your keys and stored messages. Doesn't matter if it's open or closed source.

However, open source does give users some real recourse in the event that the project moves in an undesirable direction. I don't like what's happening, I can fork it without your permission and still have access to the same development environment and build tools the original project had. I think that's important and valuable.