View source for Upload parameter
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===upload===
##0## - nobody
##[user_group]## - members of user group + admins
##1## - registered users
===upload_images_only===
##0## - allowed users can upload all allowed files
##1## - allowed users can upload only pictures, except admins
===name space===
global - all allowed users can upload
page - allowed users can upload when
1. page owner,
2. admin, or
3. allowed by ['upload'] page ACL
===overwrite===
file owner and admin can overwrite a existing file