If it is not confirmed, the volunteer submitted is the volunteer you filled in as of the deadline. If it is tampered with, the consequences are at your own risk. As long as your password is not leaked, it should be very safe to fill in volunteer information online.
However, it is said that when Guangdong province fills in its volunteers online this year, it will prompt the "Confirm All Volunteers" button, saying that this function will be temporarily turned off. This will probably be solved at school.