Configuration location for security.limit_extensions

In the website "content" settings for a website config. Where would I place the option "security.limit_extensions =" for the php-fpm.conf?

Adding it into any section currently doesn't parse for it to be included into the file. And if I edit the actual file =/etc/php/5.6/fpm/php-fpm.conf. It is re-cleaned anytime I refresh the websites in Ajenti.

Thanks