Malware seemingly in theme folder files – not sure what to do

Hello,

I have a problem with the mobile version of my site. When using the back button, it redirects to a malicious spammy webpage.

This only happens with the mobile site, and not the desktop version. Numerous people have checked the issue, and it happens consistently for every user.

I’ve been trying to find the problem, and my server hosts checked the database and found it to be clean.

They then just sent me this message, suggesting that the problem is somewhere in the newspaper theme files:

“Hello again,

Thank you for providing the credentials. I properly cleared the WP Rocket cache and installed one of the WordPress core themes, “Twenty Seventeen”. I activated this and I found that the site no longer redirected on mobile. After switching back to the Newspaper theme, the redirect came back. This suggests that the problem is part of the Newspaper theme. I am unfamiliar with this theme, but I would recommend removing the theme and reinstalling it from a known clean copy if possible. Additionally, I recommend your developer review the theme files for any obfuscated content or functions that would be causing the redirection.”

Please can you help? Have you heard of this kind of redirect problem before?

Thanks