Make sure that fields specified in filter, sortBy, etc. are model fields
and may be accessed. This is fixes a potential security issue.
The filter() function allowed guessing the content of password hashes
one character at a time.
The sort() function allowed the user to call an arbitrary method of an
arbitrary model attribute, for example sortBy=id&sortDir=distinct would
produce an unexpected error.
Marti Raudsepp
kevgliss
Kevin Glisson