Exactly. I've been saying this time and time again in the past: you cannot trust proprietary software for security, full stop. As you point out, it's security

Exactly. I've been saying this time and time again in the past: you cannot trust proprietary software for security, full stop. As you point out, it's security through obscurity (which we all know isn't really security), but what's more, you can never know if there is a backdoor in proprietary software, or if it's actually doing what it's supposed to do (and not less, or more - like logging your activity or listening in on your traffic).