Sudden RDS "[Note] Access denied for user 'root'@'xxx.xxx.xxx.xxx' (using password: YES)"

2022-09-07T03:13:15.528272Z 4105348 [Note] Access denied for user 'root'@'xxx' (using password: YES) 2022-09-07T03:13:15.555529Z 4105349 [Note] Access denied for user 'root'@'xxx' (using password: YES) 2022-09-07T03:13:15.559440Z 4105350 [Note] Access denied for user 'root'@'xxx' (using password: YES)

Suddenly, the password of the RDS was wrong as above, so access was not possible.

• Was not in AWS maintenance
• We're not working on anything
• We didn't change the password
• Monitoring figures were not unusual

Access is possible after resetting the maste* password. I've never experienced anything like this before. I'm worried that this will happen again in the future. I wonder why the password was deleted.

I'd appreciate it if you could tell me the cause and prevention method.