And @tomseys
a little helper for your test.
Copy the following code, paste it in notepad and save it as Get-WDUpdates.ps1
Then open PowerShell as Admin, go to the folder you have saved the script and run it:
.\Get-WDUpdates.ps1
This will give you a quick list of all Windows Defender updates, from the Events of your PC, hoping that you have not cleared them… 
Code:
# Get Windows Defender updates, from Windows Event logs
# Created by: Dimitri (a.k.a ddelo), 21-Nov-2018
$UpdatesQuery = @"
<QueryList>
<Query Id="0" Path="System">
<Select Path="System">*[System[Provider[@Name='Microsoft-Windows-WindowsUpdateClient'] and (EventID=19)]]</Select>
</Query>
</QueryList>
"@
$UpdateEvents = Get-WinEvent -FilterXml $UpdatesQuery
# Define a new array to gather output
$OutputCollection = @()
Foreach($event in $UpdateEvents)
{
$xml = [xml]$event.ToXml()
$Update = $xml.Event.SelectSingleNode("//*[@Name='updateTitle']") | Select -ExpandProperty '#text'
$RegEx = "KB\d*"
$KB = $Update | Select-String -Pattern $RegEx | Select-Object { $_.Matches }
$output = [PSCustomObject] @{
InstallDate = $event.TimeCreated
HotFixID = $KB.' $_.Matches '.Value
Title = $Update
}
$OutputCollection += $output | where Title -Match "Windows Defender"
}
# Output the collection sorted and formatted on screen:
$OutputCollection | Sort-Object InstallDate | FT -AutoSize
Write-Output "$($OutputCollection.Count) installed updates found, on $(Get-Date -Format g)`n"