Urgent Magento 2 403 Fix

My Magento 2 store has suddenly gone offline and is now throwing a 403 Forbidden on every front-end and admin URL. I didn’t install any new extensions, update Magento, or touch the server configuration... (Budget: $10 - $30 USD, Jobs: Apache, Debugging, Linux, Magento, Magento 2, MySQL, PHP, Website Management)