The latest changelog file for this package specifies a version in the form of 1.2-3+deb8u1, 1.2-3+nmu4 (or similar) but this does not follow from a corresponding 1.2-3 changelog stanza.
This suggests that changes were merged into a single entry. This is suboptimal as it makes it more difficult for users to determine which upload fixed a particular bug.
Refer to Debian Developer's Reference section 220.127.116.11 (Preparing packages to address security issues), Debian Developer's Reference section 5.11.2 (NMUs and
debian/changelog), Debian Developer's Reference section 5.14.3 (Direct updates to testing), and https://bugs.debian.org/916877 for details.