Is safe give write permission to site own folders

Hello, I have a website that needs write permission in its own folder to download a file from another domain and update the html

example:

wwwroot / site / views / shared / x.html

It doesn't seem to be safe, but I didn't find any documentation about it.
Does anyone have any documentation about it or am I wrong and I can release the user iis_IUSRS in the folder;