Hi, My name is Vaibhav Jain
It happened with our several clients. Actually your website is infected with some malicious code.
We need to remove this code manually. It happens when you have weak password, by using plugin or extension , sql injection attack etc.
I can resolve your issue for sure.
I can negotiate price if the number of infected files in numbers are less.
Also, we need to talk your hosting if you are on shared hosting.
Skype: vaibhavjain339