mysql – What’s causing [ERROR] Invalid (old?) table or database name ‘d:q’?

I’ve two entries in my MariaDB 10.5 error log file last night:

(ERROR) Invalid (old?) table or database name 'd:q'

I’ve looked at my nginx access log around that time and can’t see any unusual entries. I’ve searched for that error with the d:q bit and got no hits. Anyone know what this could be? Does it suggest my server has been exploited in some way…?

Thanks