Apple recommends it for all users of Mountain Lion, and says it addresses three bugs: an issue with Japanese characters in Mail, a problem with Safari accessing secure sites when Parental Controls are enabled, and an issue that could prevent Macs with more than 64GB of RAM from booting up properly.
Apparently, the updates weren’t significant enough to merit a unique OS version number of their own.
The update is available via the Mac App Store, as well as on Apple’s website. It weighs in under 30MB, and requires a restart to install.
At the same time, Apple also released OS X Lion 10.7.5 Supplemental Update, an even smaller update that Apple says resolves an issue that may cause Time Machine backups to take a very long time to complete, as well as one that prevents certain applications signed with a Developer ID from launching.