Comment by ksdev

English report: https://exatel.pl/advisory/maxthonreporten.pdf

TL;DR: It doesn't matter if you agree to join "User Experience Improvement Program" in Maxthon or not - the browser regularly sends this data to Beijing servers:

  - Windows service pack version,
  - screen resolution,
  - Maxthon version,
  - CPU freq,
  - Maxthon path,
  - adblock info,
  - startup site address,

and the most important:

  - ADDRESS OF EVERY VISITED SITE - full history, with every query entered in google,
  - every ~5 reports - FULL LIST OF INSTALLED SOFTWARE (with exact versions).