Not just Chinese ISPs. I've had Cox inject HTML/Javascript into my HTTP streams for a "test of their emergency messages system" and once for a customer survey.

Not just Chinese ISPs. I've had Cox inject HTML/Javascript into my HTTP streams for a "test of their emergency messages system" and once for a customer survey. The survey might have been a DNS redirect instead as by the time I noticed I had already navigated away from the original page and that was one of my few machines that can sometimes use my ISP's DNS. The emergency message test was HTML/Javascript directly injected into a random non-encrypted page I had loaded.