This is small bug-fix release that fixes a pretty big issue with sites getting caught in a redirect loop (Issue #674). See the 2.1.7 Milestones for specific bugs and features.
This release does not require the update script if upgrading from 2.1.6.
Please note: further development pertaining to the translation effort begun in 2.1.5 is not part of this release, but will be in future releases.