sidebar-funcs.php file in child theme folder

I have discovered a file in child theme folder (that I am sure I did not create nor upload) in an up to date WP install on a shared server named sidebar-funcs.php that contains this:

https://pastebin.com/LEGVaidn

None of the words/phrases/code, nothing in this file is remotely associable to this site…

Might anyone know what this file does/came from?

The only recent site changes in last year are WordPress updates, plugin updates, and adding the plugin ‘really-simple-captcha’ for a form.

I have deleted the file, note no changes in site functionality.

I check all sites regularly with Sucuri and none have ever been known to be compromised.

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