"Imagine if a person was in a coffee shop browsing the internet on a Windows laptop using free, unsecured wifi, explains Cylance senior researcher Brian Wallace, who discovered the vulnerability. If an attacker was able to gain access to the device through a man-in-the-middle attack, the attacker could use the vulnerability to get user credentials for a number of vulnerable apps."
In other words, the attacker would implement the hack on a compromised network and from there gain the credentials of people connecting to that network.