I've read in several places I've found via search that quarantine flag results in a warning when app is tried to be run (and then flag is cleared): https://superuser.com/questions/28384/what-should-i-do-about-com-apple-quarantine
it can ask for user confirmation the first time the downloaded program is run, to help stop malware. Upon confirmation the attribute should be removed automatically, and then the program will run normally.
What causes OS X to mark a folder as Quarantined?
When the Launch Services API is used to open a quarantined file and the file appears to be an application, script, or other executable file type, Launch Services will display an alert to confirm the user understands the file is some kind of application.
However on my MacBook (MacOS Mojave):
xattr -l /Applications/Docker.app/Contents/Resources/bin/docker
com.apple.quarantine: 01c1;5d958e46;Chrome;D01EADC9-90F1-4DAB-81A0-A96722A65A11
but I can run that app in command line with /Applications/Docker.app/Contents/Resources/bin/docker
and it works w/out warning. I also start Docker.app via Command-Space without warning now, but
xattr -l /Applications/Docker.app
com.apple.quarantine: 01c1;5d958e46;Chrome;D01EADC9-90F1-4DAB-81A0-A96722A65A11
Why I have com.apple.quarantine
attribute (not cleared already) but it has apparently no effect?