Uploaded pdf file with multiple dots (.) in name are renamed for security reason Authorized user gets an error each time when uploading a PDF with more than one dot in the name (other than the PDF extension, i.e this.is.an.example.10.pdf) but there are no disallowed extensions in the file name. 

The error says "For security reasons, your upload has been renamed to..." (surprisingly the renamed file is the SAME as the original upload name!) 
Since there are no exe php etc in the filename, why is this PDF being flagged? I searched for some time to no avail. Thanks!
when the upload file name contains multiple (.) in file name, after each dot it will be considered as extension of the file. In your case(this.is.an.example.10.pdf) it will check (is,an,examplem,10) in valid extension, It is not match with that it will add (_)inthat. If your uploaded file name is not same after drupal changes it will give that error. For more detail check file_munge_filename