This proprietary application has been under development for almost a decade. While it has had it's share of vulnerabilities as would any application it's age, they've also had that long to develop a reputation in the MacOS ecosystem. I'm no expert on LittleSnitch or Objective Development, the company behind it, but I can't remember any time they've been caught doing shady or unethical things in the time I've been using it (since about 1.x days). The last disclosed vulnerability that comes to mind (CVE-2016-8661), while being a nasty privilege escalation, was responsibly disclosed and quickly dealt with.