It IS serious:
From: https://www.krackattacks.com/#faqWe discovered serious weaknesses in WPA2, a protocol that secures all modern protected Wi-Fi networks. An attacker within range of a victim can exploit these weaknesses using key reinstallation attacks (KRACKs). Concretely, attackers can use this novel attack technique to read information that was previously assumed to be safely encrypted. This can be abused to steal sensitive information such as credit card numbers, passwords, chat messages, emails, photos, and so on. The attack works against all modern protected Wi-Fi networks. ...As a proof-of-concept we executed a key reinstallation attack against an Android smartphone. In this demonstration, the attacker is able to decrypt all data that the victim transmits. For an attacker this is easy to accomplish, because our key reinstallation attack is exceptionally devastating against Linux and Android 6.0 or higher.
Wifi simply is not safe for most mobile devices, even if you don't use your phone/tablet for financial transactions. as HoTiCE points out in his excellent post above.. I still use it but I have no trace on my devices of any of the financial institutions I deal with. I have a Windows laptop for banking when I travel (Windows has some kind of fix to prevent KRACK attack) and only use it in a pinch when on friends' networks, not public networks.
As you can see from this list of routers, fixes are few and far in between although the companies are taking the threat very seriously. https://github.com/kristate/krackinfo#v ... e-complete