Disabling Debug Mode (reloading config.php)

Several months ago we completed a major upgrade from Xenforo 1.4 to 2.2. For whatever reason, debug mode was enabled after the upgrade and has been enabled on our live site ever since. I am now learning that's not good. I have changed the debug variable to 'false" in the /src/config.php file, but debug mode is still active.

Do I need to reboot our server to get config.php to reload or is there a less invasive way?

Also, what liabilities have we exposed ourselves to by having debug mode...