Versions of Office that bypass the official installation process are often unofficial "cracked" software.
This is the most significant risk. Cybercriminals know that "Office 2019 portable" is a highly searched term. They package cryptominers, ransomware, keyloggers, or botnet clients inside a fake WordPortable.exe .
However, you can still achieve a "no-install" experience or use Office on the go through official, safe methods. 1. The Official "No-Install" Way: Microsoft 365 for the Web