Filling the inputs of SecurityAgent if they exist?
This worked

set appName to "username"
set appPass to "password"

tell application "System Events"
    repeat while exists (processes where name is "SecurityAgent")
        tell process "SecurityAgent"
            if exists (text field 1 of window 1) then
                set value of text field 1 of window 1 to appName
                set value of text field 2 of window 1 to appPass
            end if
            click button "Allow" of group 1 of window 1
        end tell
        delay 0.2
    end repeat
end tell