I have been getting these oriental characters appearing across my browser tabs in Firefox. Sometimes there are only one or two characters, sometimes all the way across the screen. I did a screen capture and printed the results and took it to a Chinese person. He said that they are not really Chinese characters, just 'computer-generated' characters, some Chinese, some perhaps others, some ???.
In Firefox [Win 8.1] I go to the 'View' drop-down menu and change 'Character Encoding' from 'Unicode' to 'Western'. This may be a deterrent, but I note that some web sites [ATT / Yahoo e.g.] can change the setting back to 'Unicode'... which makes it an on-going process.
When I have some secure traffic to accomplish I try to just drop Firefox and then reload it. I have no idea if this aberration means I am hacked by Chinese, N. Korean, Martian, etc. invaders and I am giving up my private security info. Very disconcerting.
I am here because I did a net search to see if others are having this problem.
I also want to mention that - at least in Firefox - the phenomenon occurs when I click on a link on a web page; first small righ-angle arrows appear on both sides of the browser tab, then the foreign characters begin to proliferate. I cannot imagine why MS or McAfee has not discovered this invasion and addressed it.
Miffed!