I'm guessing if you've seen something like this before, you know what it is.
Personally, I don't know where to start with describing this issue other than it looks like all of my standard output is somehow going to the console.
From what I can tell, this stuff is not called in my code, but then I generally work with Windows Forms, not ASP.NET.
I don't typically debug using localhost, but I wanted to make sure I had a lot of ASP.NET login security features removed before updating my personal website.
Here's what I see when I debug in localhost: