Find an embedded XML file inside a spreadsheet

We are being told by our security team that the firewall of all things is reporting that a sharepoint file is infected with a virus.   The file name is just Workbook.xml, and that's all that they have.  We've searched the SP system for that file name and can't find anything, so we are assuming that it's embedded somewhere in a spreadsheet.

Does anyone know of a way to search for an embedded XML file within a spreadsheet?  I was trying to find a powershell command that would do that, but am coming up short.

This is onprem SP2013.

Any help is appreciated.

Ted