I've been tearing my hair out trying to get rid of the quarantine "Do you want to open this?" warning because I don't like it.
The well documented way (defaults write com.apple.LaunchServices LSQuarantine -bool NO) does NOT work.
Also, I've used the Secrets Preference pane and that doesn't work either. As soon as I uncheck the box and close the pane and reopen, it's still checked.
(I've tried rebooting right after these methods, no dice.)