Easy way to tell what updates/upgrades have been applied:
Login thru putty
Open a command line
type: sysinfo -i

You should see something like this:
bash-3.2$ sysinfo -i
 
Product information
-------------------
Version: 11.6.1.48
Product: UM8000
 
Update information
------------------
Wed Oct  5 15:31:49 GMT+7 2011:UPDATE:Update from 11.3.0.37 to 11.4.0.24
Thu Mar 15 08:02:39 GMT+7 2012:UPDATE:Update from 11.4.0.24 to 11.5.0.54
Mon Jun 25 15:33:30 GMT+7 2012:UPDATE:Update from 11.5.0.54 to 11.5.1.61
Tue Jul 10 11:35:54 GMT+7 2012:UPDATE:Update from 11.5.1.61 to 11.5.1.61
Fri Aug 31 11:18:43 GMT+7 2012:Update 14512-15296-11.5.1.61-em.sh applied.
Thu Nov  1 11:13:43 GMT+7 2012:UPDATE:Update from 11.5.1.61 to 11.6.0.29
Fri Feb  1 09:22:19 GMT+8 2013:UPDATE:Update from 11.6.0.29 to 11.6.0.31
Mon Mar 25 12:32:25 GMT+7 2013:Update 14861-15738-11.6.0.31-em.sh applied.
Fri Jun 14 09:06:00 GMT+7 2013:UPDATE:Update from 11.6.0.31 to 11.6.1.48
Fri Jul 19 11:03:07 GMT+7 2013:Update 15233-16053-11.6.1.48-em.sh applied.