FULL PRODUCT VERSION :
java version "1.8.0_51"
Java(TM) SE Runtime Environment (build 1.8.0_51-b16)
Java HotSpot(TM) 64-Bit Server VM (build 25.51-b03, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Mac OS X Yosemite Version 10.10.3 (14D136)

A DESCRIPTION OF THE PROBLEM :
A dialog came up advising me there was a newer version of Java. I clicked Install and it went through its paces, ending with an alert informing me that JDK 8 update 51 was installed. The problem is, it wasn't. When I listed the Java version, no update 51.

$ ls -l /Library/Java/JavaVirtualMachines/
total 0
drwxr-xr-x 3 root wheel 102 Sep 7 2011 1.6.0_27-b07-393.jdk
drwxr-xr-x 3 root wheel 102 Mar 18 2014 jdk1.7.0_51.jdk
drwxr-xr-x 3 root wheel 102 Jun 12 2014 jdk1.8.0_11.jdk
drwxr-xr-x 3 root wheel 102 Nov 4 2014 jdk1.8.0_25.jdk
drwxr-xr-x 3 root wheel 102 Jun 7 11:38 jdk1.8.0_45.jdk
$

I couldn't find a newer version by any other means, so I went to the website and downloaded the disk image for update 51.

http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html

This installed without issue, and now the update is present.

$ ls -l /Library/Java/JavaVirtualMachines/
total 0
drwxr-xr-x 3 root wheel 102 Sep 7 2011 1.6.0_27-b07-393.jdk
drwxr-xr-x 3 root wheel 102 Mar 18 2014 jdk1.7.0_51.jdk
drwxr-xr-x 3 root wheel 102 Jun 12 2014 jdk1.8.0_11.jdk
drwxr-xr-x 3 root wheel 102 Nov 4 2014 jdk1.8.0_25.jdk
drwxr-xr-x 3 root wheel 102 Jun 7 11:38 jdk1.8.0_45.jdk
drwxr-xr-x 3 root wheel 102 Jul 21 11:57 jdk1.8.0_51.jdk
$

The Runtime version above is the result of executing

$ /Library/Java/JavaVirtualMachines/jdk1.8.0_51.jdk/Contents/Home/bin/java -version



ADDITIONAL REGRESSION INFORMATION:
Truly, I'm not sure it ever worked.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
See Description

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Install the new JDK version
ACTUAL -
Didn't install

REPRODUCIBILITY :
This bug can be reproduced always.

CUSTOMER SUBMITTED WORKAROUND :
Use the website