When I run journalctl -xe I can see:

May 28 15:02:20 <Hostname> mariadbd[3536598]: 2024-05-28 15:02:20 500984 [Warning] Access denied for user ''@'localhost'
May 28 15:02:20 <Hostname> mariadbd[3536598]: 2024-05-28 15:02:20 500985 [Warning] Access denied for user ''@'localhost'
May 28 15:02:20 <Hostname> mariadbd[3536598]: 2024-05-28 15:02:20 500986 [Warning] Access denied for user ''@'localhost'
May 28 15:02:20 <Hostname> mariadbd[3536598]: 2024-05-28 15:02:20 500987 [Warning] Access denied for user ''@'localhost'
May 28 15:02:20 <Hostname> mariadbd[3536598]: 2024-05-28 15:02:20 500988 [Warning] Access denied for user ''@'localhost'
May 28 15:02:20 <Hostname> mariadbd[3536598]: 2024-05-28 15:02:20 500989 [Warning] Access denied for user ''@'localhost'
May 28 15:02:21 <Hostname> mariadbd[3536598]: 2024-05-28 15:02:21 501008 [Warning] Access denied for user ''@'localhost'
May 28 15:02:21 <Hostname> mariadbd[3536598]: 2024-05-28 15:02:21 501009 [Warning] Access denied for user ''@'localhost'
May 28 15:02:21 <Hostname> mariadbd[3536598]: 2024-05-28 15:02:21 501010 [Warning] Access denied for user ''@'localhost'

…and so on.

Over once per second! I have many websites running on this server, but thing is — they are all working properly!
Although overall everything seems to be working fine, I feel a little uneasy about it… Could anyone please provide any suggestions as to why this is happening and how to fix this behavior?

Thank you in advance!

I googled why this happens but found nothing.