Virus on the site?

Question

Malware

Good afternoon! I had an opportunity :)
And so, let's start:
1) I made a website, then I noticed that on it only from mobile devices in the layout appears such a little thing with the inscription advertising

I did not find the cause of this bug.
2) I went to the second site, and here I see the good old inscription . I

used:
- Bootstrap 4
- PHPMailer
- MaskInput (Phone input mask plugin) I
suspect that the problem is in one of the plugins.
And what can you say? Have you ever faced such a problem?

Answer 1

advertising on the mobile Internet through Megafon
https://habrahabr.ru/post/318010/
https://roem.ru/22-11-2017/263731/reklamnoe-pravo-...

Answer 2

that is the mobile Chukhons, who are megabon biblan and tilitili2. they spam..
Author! Yuzay wired Internet through the waffle, no problem ...