I was using Opera Mini on my phone to read this article and opened this link in another tab.

Upon switching to the tab, I was presented with the operator's content lock screen (not entirely sure what filter that falls under, but that's besides the point). Strange, I though Opera Mini used an encrypted tunnel between the browser on the phone and Opera's compression/proxy servers? If that's the case, how on Earth does can the operator know what's inside the tunnel, and how are they inserting their web page???

I did a bit of experimenting and it seems HTTP mode causes the block every time, while HTTP/Socket mode causes it intermittently, with the page occasionally making it through.

Any ideas what's going on here?