According to the researcher: "The TLS connections are encrypted against tampering or eavesdropping. However, the application does not validate the server certificate properly while initializing the TLS connection. This allows for a network attacker to intercept the connection and read the data. The attacker could the either send the client a malicious response, or forward the (possibly modified) data to the real server."
https://support.google.com/product-documentation/answer/14950962?sjid=9489879942601373169-NA