Apple - how to avoid the "downloaded application" warning for a Standard User

The basic problem is that the applications are all marked as being in quarantine (they have the "com.apple.quarantine" extended attribute) because they were downloaded from the net. Running the app removes the quarantine attribute if the file permissions allow you to modify the file (e.g. if you're the file's owner -- in this case, the Admin user). If you don't have permission, the quarantine attribute stays, and you keep getting the "downloaded from the Internet" message over and over.

Solution: one way or another, you need to remove that quarantine attribute. You can do this for a bunch of apps at once in Terminal.

1. First use su (switch user) to switch to your admin user (type in "su", then a space, then the account name of your admin user, then press return and enter the admin account's password; note that the password won't be displayed as you type). It should look something like this:

   Dans-Mac:~ dan$ su adminacct
   Password:
   bash-3.2$
   

2. If that works, type in "xattr -r -d com.apple.quarantine", then a space, then drag all the apps you want to dequarantine from the Finder to the Terminal window; when they're all listed, press return. Note that you can drag them one at a time or in groups, whatever's convenient. Something like this:

   bash-3.2$ xattr -r -d com.apple.quarantine /Applications/BBEdit.app /Applications/Firefox.app