If your domain when uploading a page, for example the Home page, suddenly shows unwanted windows or a request to install dialer or, worse, you are warned by your antivirus system that there is a virus, the reason lies in the carrying out of external code.
The external code is carried out through the provided scripts inadvertently entered (maybe as a test) in the pages: usually they are scripts for
-statistics
-counters
-any .js called back on external website.
These scripts cannot be checked in any way and must be carefully avoided, so not to have any surprises.