If the USB drive is infected, running portable Office can:
Because of this, (VSTO, Office.js web add-ins, COM shims, VBA compiled modules) may fail or behave unpredictably on portable editions. Portable Microsoft Office 2019
Because of this, Any “portable” version you find online is, by definition, a hack or a repack. If the USB drive is infected, running portable
End of support for Office 2016 and Office 2019 | Microsoft Support If the USB drive is infected
Using "portable" versions usually bypasses Microsoft's Licensing Agreement (EULA), which can be a legal risk for business users. Better (and Safer) Alternatives