The best tool for replacing strings is Perl. It can even do it for multiple files. You don’t need to know much Perl to use the “Perl PIE” technique, that turns a potentially long script into a one-liner. I used it to start an SEO task on this site.
This is for any CMS, but I needed to add an automatic backup when I migrated a site to WordPress. Most folks use a plugin, but I’m old-school and like to use cron. You need to know some Unix to implement this.