Release 5.18.3
Release 5.18.3 is release 5.18.2 rolled out to all ConnectiveOne instances. It contains no new features or fixes compared with 5.18.2: only the version number changed.
If your instance moved to 5.18.3 from version 5.17.2, you received all changes of releases 5.18.0 and 5.18.2 — they are described in the release 5.18.0 notes and the release 5.18.2 notes. Be sure to review the "Please note" sections in both.