PaulTon: It appears in main page and game client without warning.
Paul, I play using Slimjet (Chromium) browser, but watch videos on Maxthon (some won't play on Slimjet/Chrome for some reason). I noticed the other day a similar pop-up, and then I was redirected for no reason. I wasn't watching a vid at the time, either. On my malwarebytes, I have "treat all all PUPS" and "PUMS" as malware, and have all 3 boxes checked as shown.
Every time I use maxthon now to watch videos, I run mbam towards the end and it finds 4-5 things every time. I wanted to see if it was the videos, so I just signed into maxthon (wgt), and ran a scan while not clicking anything. 9 minutes and same 4-5 hijacks came up. I then tried IceDragon, and nothing, Slimjet and nothing. I seriously believe Maxthon is the problem. I may be wrong, but I have decided to remove it. And I haven't had a problem since (3 days now). Maxthon doesn't offer any decent extensions, nor is it very safe. It's just wide open. Their adhunter is a joke. I have never seen an ad anywhere, on any site, until Maxthon.
But, everyone's tastes are different, too.