Folder with 777 what htaccess rules do I use to whitelist?
I have an uploads folder with permissions set to 777 (cannot be changed).

In this, I allow trusted users to upload images.  

I want to only allow .jpg,.png,.gif files into this folder.

How can I do this (with .htaccess?)?
Folder with 777 what htaccess rules do I use to whitelist?
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I have an uploads folder with permissions set to 777 (cannot be changed).

In this, I allow trusted users to upload images.  

I want to only allow .jpg,.png,.gif files into this folder.

How can I do this (with .htaccess?)?