If dl.file.extensions is not equals with * the Basic Document uploader will trigger the following error e.g: when the only acceptable extension is pdf: "Document names must end with one of the following extensions: .pdf."
Steps to reproduce:
1.) set dl.file.extensions=.pdf in portal-ext.properties
2.) start the portal
3.) log in and navigate to Control Panel > Documents And Media
4.) select Add > Basic Document
5.) select a .pdf file from the file system
6.) set title e.g.: my basic document
7.) press Save
expected behavior: file is uploaded with the title "my basic document"
real behavior: user receives error message that he/she have to upload .pdf document
reason: extension is validated against the title during add procedure