Research and Development
There is a not widely known COM object that you can use to list all the installed Windows Updates on a machine.
Here is the code:
$Session = New-Object -ComObject Microsoft.Update.Session
$Searcher = $Session.CreateUpdateSearcher()
$HistoryCount = $Searcher.GetTotalHistoryCount()
$Searcher.QueryHistory(1,$HistoryCount) | Select-Object Date, Title, Description