Hi Lance,
It wasn’t just siteground that flagged it. I originally got the flag from Google Search Console. That is what made me go to Siteground to do a security scan.
Siteground did not quarantine the file, I enabled the security scan after I realized I had an issue to help me find the issue. I deleted matomo plugin and the scan and google both came back clean once Matomo was removed.
I am not sure Siteground is part of the issue or if it is a coincidence we both have them as a host. Again, Google Search Console is the one who originally found the threat.
Tom