Don't allow fingerprinting via navigator.userAgent
Reporting real operating system in navigator.userAgent is a bug because of the following:
Since you introduced this anti-privacy feature (by "anti-privacy feature" I mean reporting real OS in navigator.userAgent property), you must provide a way to disable it. Otherwise it looks like an intentional action against all Tor Browser users who want to keep their privacy protected. Users may want to stop reporting real OS. Users didn't gave you a permission to decide it for them. There are many websites which rely on navigator.userAgent and don't use any other fingerprinting methods. Currently Tor Browser users can't stop them from reading real OS version from navigator.userAgent. It's a bug, and it's must be fixed.
According to specifications, navigator.userAgent must be equal to HTTP User-Agent header. https://html.spec.whatwg.org/multipage/system-state.html#dom-navigator-useragent https://fetch.spec.whatwg.org/#default-user-agent-value Any difference between HTTP User-Agent and navigator.userAgent is spec violation.