Natively, SafeCracker doesn't support HTML5 attributes on it's form tag.
This extension allows you to use data-foo="bar", autocomplete="no" and novalidate="novalidate".
Authors: Objective HTML and Jason Varga.
In EE 2.7, Safecracker was renamed to Channel Form.
Toby Stokes has created a fork which works for 2.7+.
https://github.com/tobystokes/EE-SafeCracker-HTML5-Attributes