Dropbox Releases iOS Update 3.5, Includes Touch ID

Dropbox released version 3.5 Monday, a free update with notable new features. This release includes support for the iPhone 6 and 6 Plus, as well as Touch ID support to unlock access to Dropbox. There's also a fix for an issue previewing RTF files and "general stability and performance improvements." 

This is a free update to a free app (which offers in-app purchases for extra space), and should be available everywhere via the usual channels.