Hi povezise,
There is a plugin that can remove the ‘Proudly Powered by’:
Remove “Powered by WordPress“.
I can understand you want to do that from security reasons.
There is also a way to remove the wordpress branding completely from login pages etc. with this plugin: Remove WP Branding
However you do this it’s nice for the makers if you leave the Theme made by notice as a ‘thank you’, you are still using this theme for free..
unless you have paid for the pro and thus can remove the notice.
You can however edit the theme files directly and remove it from the code.
Removing this in the code will only make it return with every update.
So best not do that if you want a permanent solution.
If you like the theme, and want to do this, there is only on option to do this.
and that is to buy it.
Love,
Amy