Hi, it's my job!
I think this problem is raised from the code which has a backdoor attached, they will be able to attack and hack your site again after someone fixed it. Your site needs to be scanned. Please message me to get started.
My bio: I'm a Drupal themer/developer, I have over 6 years working on various Drupal projects from (Design, HTML, CSS, Javascript) to development (PHP, MYSQL, Drupal). I can create new themes, fix theme issues and module issues, create and upgrade Drupal sites, also suggest the best solution for Drupal site owners.
Thanks,
Dang