Where did this code come from?

Question

PHP

My cat decided to go through the keyboard and press the F12 button, thereby opening the console. I saw there EXTRA code that I did not write. Where is he from? I've looked all over the internet, but there's nothing! I didn't use any JS scripts.

In all browsers =.=

Answer 1

1) Browser extension
2) Chinese "antivirus"
3) Hoster

Answer 2

Can throw provider, hoster, virus on the site.
Write at least where you are launching the site - locally or on the Internet?

Answer 3

Most likely you have picked up malware, it is difficult to deal with this problem, but it is possible.
See if there are extensions unknown to you in the browser. Delete everything you didn't install. Especially something that is not from an off source. If after restarting the browser / computer they reappear, then you need to look for the installed software. The easiest way is to look in the Control Panel-Programs and remove what you did not install there. Pay attention to programs that do not have a publisher. Well, cleaning the autorun is also not bad)
Good luck in this difficult struggle =)