loofah version 2.1.0 has been released!
TL;DR: CSS property parsing and sanitization has been re-implemented on top of Crass:
replacing the regexes that were lifted from html5lib back in 2009. I’m relatively sure this is a good thing.
Note that Loofah underlies Rails sanitization since 4.2, so please do let me know via Github issue if this breaks any behavior for you. (Also note that this change has been available in RCs since August 2015.)
Full changelog below.