Conceivably: If you have MITM and can inject... you'd next need web browser 0day exploit chain w/ sandbox escape and then a stealthy trojan to install. This wou

Conceivably: If you have MITM and can inject... you'd next need web browser 0day exploit chain w/ sandbox escape and then a stealthy trojan to install. This would obviously be quite the capability and require a lot of maintenance to work cross-browser, cross-OS, and evade security products / built-in security features. It is definitely possible however.