Drupal 7.44 upgrade to newer secure version + antivirus check

We have Drupal, which was created before 2018 and is an activation service for one of our products. This product installs on Windows and on first startup it contacts this Drupal via http address, loading a registration or login form frame from Drupal. User management is based on the Drupal database.

The site works without errors when set to php5.6. Changing to 7.0 generates small error messages, but functionality is preserved. When changing to 7.2 there are already such messages:

Deprecated function: The each() function is deprecated. This message will be suppressed on further calls in menu_set_active_trail()

We are currently working on php7.0 version.

The site recently went viral, but we managed to delete the problematic files. it is now functioning properly. However, the scanners still show the presence of the virus.

The site is added to Installatron and regular copies are made. In case of failure when trying to upgrade, it will be possible to o undo the changes.