1.1.13 is available here (and via apt-get install kuvert in debian and ubuntu).

Changes: the pgp-signature part is now tagged a bit more extensively with a content-description and the "canonical" filename; while the filename tag was there in an earlier version (and got removed for reasons lost in time), the content description might help the more...suboptimal mail clients out there.

The prod to do this came from Andreas Labres.