Hi Aliya,

Both files are from Joomla Core - we didn't touch them, so your question is to Joomla Developer team or forum.joomla.org > Category "Security in Joomla! 5.x". But peronsally I doubt about malware/virus inside them.

1. Just update Joomla to current version 5.3.1 if you used Quickstart with older J! inside.
2. Or reinstall Joomla core. And then all files will be overriden by orginal content. Or use FTP and override those two files using FTP and Joomla_5.3.1-Stable-Update_Package.zip
3. Then rescan files again.

Yes, anti-virus software sometimes generates false alarms.

You can share also more details about what "issue" was found, in which line - just out of my curiosity.