HereWeFix

Use the below command to remove the entries for application pools that have no domain-related from the Plesk database.
Solution:
1.If you have an issue on a remote server, connect your server through RDP.
2.Open the command prompt and run the below command.
DELETE i, ia FROM IisAppPools i LEFT JOIN IisAppPoolDomains ia ON i.id = ia.poolId LEFT JOIN domains d ON d.id = ia.domainId WHERE d.name IS NULL AND i.id != 1;

The issue occurred while deleting the domain from the Plesk panel. It happens due to database inconsistency. Follow the below steps to resolve the issue.

Solution:
1.If you have an issue on a remote server, connect your server through RDP.
2.Open the command prompt and generate a backup for the Plesk database
  plesk db dump psa > C:\psa_dump.sql
3.Connect Plesk database
  plesk db
4.Check whether there is no domain associated with such ID in the Plesk database. Replace 1381 with your affected ID.
  select * from domains where id=1381;
NOTE: if you got the below output then the given ID is not available in the database.
              Empty set (0.00 sec)
5.Fix the inconsistency in the Plesk database.
  delete from IisAppPools where ownerId=1381;
6.If you disabled ModSecurity activate and check.

Check all user's password expiry date except system users on Linux based system.
for user in $(cat /etc/passwd |cut -d: -f1); do echo $user; chage -l $user | grep "Password expires"; done | paste -d " "  - - | sed 's/Password expires//g' | grep -v "never"

Below command will help to find everything in /var/www/html and set to read-only.

find /var/www/html -iname "*" -print0 | xargs -I {} -0 chattr +i {}