1.8.8 is an update to Java Edition that was released on July 28, 2015 to mainly fix security bugs. 1.8.8 is compatible with servers running 1.8–1.8.7. While it was not the last update to 1.8, it was the last one before the snapshots of 1.9 started.
A pre-release for 1.8.8 was released on July 27 for players to test, though the full release of 1.8.8 is identical to this pre-release.