Client still using internet explorer

I was testing a new load of stress on my setup and the League Client showed me a white background with some text, in the form of a notepad .html page (one of those cheap ones that took you 5 minutes to pass some time, etc).

The text was my password but I'm unsure of anything else that might be there, it was only up for a second and I was expecting nothing out of the ordinary. This was as the client loads up from its splash art. Side note: if I disconnect my internet or switch WiFi whilst on the clients' login page, everything shifts upwards. By this I mean the bottom half of my screen (where it has the password box and some "forgot your username/password" and "create your account", whatever) is taking up the top 25%, as in it has been moved upwards, though the window hasn't been moved. Like the browser having this text at the top of the screen with the task bar underneath it at the quarter-way mark and the rest looping around to have the now-top be at the bottom.

Either way, this is another page made literally in plaintext .html, alike the homepage/store page that sometimes goes white, if anyone has seen that. This showed me my own password in plain sight, and that could be abused. Note that I have "Remember Me" checked.

I'm posting it here for people to test it out more, whoever tests this out. Riot can be aware of this, players can, it's up to whoever uses it in which way to do whatever you want to do with what is found.