This is nothing to really worry about. Nothing malicious has been installed on your computer. All you are seeing is the browser's cache files (the local store of the website files). The file is part of the website, done entirely in JavaScript. It is not harmful to you, except that it uses some of your CPU (just like any other JavaScript on a website). It is, however, a possible annoyance for you, since it is using your computer's CPU to make money for someone else without your permission. You should avoid any website that intentionally uses this tactic. Or alternatively, you should report it to the owner of the website, since it could be a mistake, or some malware that was installed in the website as a result of their website being hacked.