Unknown File Type Vulnerability in Google Quickshare

Summary

There exists an auth bypass in Google Quickshare where an attacker can upload an unknown file type to a victim. The root cause of the vulnerability lies in the fact that when a Payload Transfer frame of type FILE is sent to Quick Share, the file that is contained in this frame is written to disk in the Downloads folder. Quickshare normally deletes unkown files, however an attacker can send two Payload transfer frames of type FILE and the same payload ID. The deletion logic will only delete the first file and not the second. We recommend upgrading past commit 5d8b9156e0c339d82d3dab0849187e8819ad92c0 or Quick Share Windows v1.0.2002.2