Folder Permission Security?

[Theoddity]

I've created a password protected php content management tool for a customer. One script lets the customer upload photos to one particular directory. I have to set that one folder's permission to "write" for "all users" in order for the photo to upload. I was wondering if this creates a security hole for others outside the server to get into that folder that has write permissions?

(The php script is password protected so that only those with passwords can get to the file upload script.)