Hello,
How to deactivate the quarantine :
Since 10.15, Catalina, Mac OS X is equipped with a quarantine system for downloaded files.
To prevent this alert message from appearing when opening a file that has already been downloaded, enter the command `
xattr -d -r com.apple.quarantine ~/Downloads
In the Terminal, taking care to replace ~/Downloads with the folder you wish to act on. The execution of this command may take some time, especially in the case of a dense tree of multiple small files. It is useful to keep a good balance between general security and comfort when working on a set of files.
To completely disable the quarantine, execute the command
defaults write com.apple.LaunchServices LSQuarantine -bool NO
Then restart your Mac. To go back, simply replace NO with YES. Be aware, however, that you will then be working without a safety net - just like in previous versions of OS X.
Enjoy,
Jerome