Firefox (differential) MAR updater

#Requires -Version 2.0
# Refer to https://wiki.mozilla.org/Software_Update:Manually_Installing_a_MAR_file
# Applies newest downloaded update from $OUTSIDE folder
# I do very few checks, you should know what you're doing
# Tested with http://archive.mozilla.org/pub/firefox/releases/58.0.2/update/win64/ru/
# Greetings from ALTracer
#
# UAC elevating...
If (-NOT ([Security.Principal.WindowsPrincipal][Security.Principal.WindowsIdentity]::GetCurrent()).IsInRole([Security.Principal.WindowsBuiltInRole] "Administrator"))
{ $arguments = "& '" + $myinvocation.mycommand.definition + "'"
  Start-Process "$psHome\powershell.exe" -Verb runAs -ArgumentList $arguments
  break }
# CHANGE YOUR DIRS
$OUTSIDE = "D:\Install\ff"
$APP = "C:\Program Files\Mozilla Firefox"
# assuming current user has write access over there:
Set-Location $OUTSIDE
$latestmar = Get-ChildItem -Path $OUTSIDE -Name *.mar | Sort-Object LastWriteTime -Descending | Select-Object -First 1
Copy-Item -Force $latestmar update.mar
$latestasc = Get-ChildItem -Path $OUTSIDE -Name *.asc | Sort-Object LastWriteTime -Descending | Select-Object -First 1
Copy-Item -Force $latestasc update.mar.asc
Copy-Item -Force $APP\updater.exe updater.exe
Copy-Item -Force $APP\updater.ini updater.ini
# now we must be UAC elevated
Set-Location $APP
Start-Process -Wait -FilePath $OUTSIDE\updater.exe -ArgumentList "$OUTSIDE `"$APP`" `"$APP`""
$status = Get-Content $OUTSIDE\update.status
if ($status -eq "succeeded")
{ Remove-Item $APP\uninstall\uninstall.update
  Copy-Item -Force $OUTSIDE\update.log $APP\uninstall\uninstall.update
  Start-Process -Wait -FilePath "`"$APP\uninstall\helper.exe`"" -ArgumentList "/PostUpdate"
  Read-Host "Updated, I guess"}
else
{ type $OUTSIDE\update.status
  Read-Host "Error applying update! Check update.log" }
# cleanup
Set-Location $OUTSIDE
Remove-Item updater.ini
Remove-Item updater.exe
Remove-Item update.mar
Remove-Item update.asc