Block Excel XLL Add-ins that come from an untrusted source
Verified with Microsoft 365/Office 5568.1000 — updated on September 4, 2026
Supported on: At least Windows Server 2016, Windows 10
Path in the GPO console
User Configuration\Administrative Templates\Microsoft Excel 2016\Excel Options\Security\Trust Center Description
This policy setting allows you to block Excel XLL Add-ins that come from an untrusted source. If you enable this policy setting, you can set one of these options: - Block: XLL add-ins from untrusted sources are blocked. Users will receive a notification that the add-in was blocked. - Show Additional Warning: Show an additional warning prompt after the user chooses to enable an XLL add-in from an untrusted source. - Allow: XLL add-ins from an untrusted source are allowed. The exceptions when Excel XLL Add-ins will be allowed to run are: - The XLL is stored in a Trusted Location. - The XLL is digitally signed and the matching Trusted Publisher certificate is installed on the device. If you disable this policy setting, the settings configured in the Macro and Add-in Settings sections of the Trust Center determine whether Excel XLL Add-ins that come from an untrusted source will be allowed. If you disable or do not configure this policy setting, users will be able to override default behavior by modifying the registry. For more information, see https://support.microsoft.com/topic/1e3752e2-1177-4444-a807-7b700266a6fb.
Registry
software\policies\microsoft\office\16.0\excel\security Export Builder
BETAConfigure the state, scope and options, then generate .reg, PowerShell, Intune and SCCM outputs — or add the setting to a multi-setting collection.
These exports write the registry — this is not a managed GPO. ⓘ
.reg file
Windows Registry Editor Version 5.00
; Exported from gporais.com
; Policy: Block Excel XLL Add-ins that come from an untrusted source
; State: Enabled
; Supported on: At least Windows Server 2016, Windows 10
[HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\excel\security]
"blockxllfrominternet"=dword:00000001More formats (PowerShell, Intune, SCCM)
PowerShell
# Exported from gporais.com
# Policy: Block Excel XLL Add-ins that come from an untrusted source
# State: Enabled
# Supported on: At least Windows Server 2016, Windows 10
# Warning: In SYSTEM context (the Intune default), HKCU targets the SYSTEM profile. Run this script using the logged-on credentials.
$path = 'HKCU:\software\policies\microsoft\office\16.0\excel\security'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'blockxllfrominternet' -Value 1 -Type DWordIntune XML
No direct Policy CSP / OMA-URI mapping for this policy. Use the Intune Remediation tab, or ingest the ADMX in Intune.Intune Remediation
# === Detection script ===
# Exported from gporais.com
# Policy: Block Excel XLL Add-ins that come from an untrusted source
# State: Enabled
# Supported on: At least Windows Server 2016, Windows 10
# Warning: In SYSTEM context (the Intune default), HKCU targets the SYSTEM profile. Run this script using the logged-on credentials.
function Test-RegistryValue {
param(
[Parameter(Mandatory = $true)][string]$Path,
[Parameter(Mandatory = $true)][string]$Name,
[object]$Expected,
[ValidateSet('String', 'DWord', 'MultiString')][string]$Kind = 'String',
[switch]$Absent
)
try {
$item = Get-ItemProperty -LiteralPath $Path -Name $Name -ErrorAction Stop
} catch {
return $Absent.IsPresent
}
if ($Absent.IsPresent) { return $false }
$actual = $item.$Name
if ($Kind -eq 'DWord') { return ([int64]$actual) -eq ([int64]$Expected) }
if ($Kind -eq 'MultiString') {
$actualValues = @($actual)
$expectedValues = @($Expected)
if ($actualValues.Count -ne $expectedValues.Count) { return $false }
for ($i = 0; $i -lt $expectedValues.Count; $i++) {
if ([string]$actualValues[$i] -ne [string]$expectedValues[$i]) { return $false }
}
return $true
}
return [string]$actual -eq [string]$Expected
}
$checks = @(
(Test-RegistryValue -Path 'HKCU:\software\policies\microsoft\office\16.0\excel\security' -Name 'blockxllfrominternet' -Expected 1 -Kind DWord)
)
if ($checks -notcontains $false) {
Write-Output 'Compliant'
exit 0
}
Write-Output 'Non-compliant'
exit 1
# === Remediation script ===
# Exported from gporais.com
# Policy: Block Excel XLL Add-ins that come from an untrusted source
# State: Enabled
# Supported on: At least Windows Server 2016, Windows 10
# Warning: In SYSTEM context (the Intune default), HKCU targets the SYSTEM profile. Run this script using the logged-on credentials.
$path = 'HKCU:\software\policies\microsoft\office\16.0\excel\security'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'blockxllfrominternet' -Value 1 -Type DWordSCCM scripts
# Exported from gporais.com
# Policy: Block Excel XLL Add-ins that come from an untrusted source
# State: Enabled
# Supported on: At least Windows Server 2016, Windows 10
# SCCM Configuration Item guidance:
# Create a Configuration Item of type "Setting: Script".
# Discovery script: use the Detection script below.
# Remediation script: use the Remediation script below.
# Compliance rule: the Discovery script output equals 'Compliant'.
# === Detection script ===
# Exported from gporais.com
# Policy: Block Excel XLL Add-ins that come from an untrusted source
# State: Enabled
# Supported on: At least Windows Server 2016, Windows 10
# Warning: In SYSTEM context (the Intune default), HKCU targets the SYSTEM profile. Run this script using the logged-on credentials.
function Test-RegistryValue {
param(
[Parameter(Mandatory = $true)][string]$Path,
[Parameter(Mandatory = $true)][string]$Name,
[object]$Expected,
[ValidateSet('String', 'DWord', 'MultiString')][string]$Kind = 'String',
[switch]$Absent
)
try {
$item = Get-ItemProperty -LiteralPath $Path -Name $Name -ErrorAction Stop
} catch {
return $Absent.IsPresent
}
if ($Absent.IsPresent) { return $false }
$actual = $item.$Name
if ($Kind -eq 'DWord') { return ([int64]$actual) -eq ([int64]$Expected) }
if ($Kind -eq 'MultiString') {
$actualValues = @($actual)
$expectedValues = @($Expected)
if ($actualValues.Count -ne $expectedValues.Count) { return $false }
for ($i = 0; $i -lt $expectedValues.Count; $i++) {
if ([string]$actualValues[$i] -ne [string]$expectedValues[$i]) { return $false }
}
return $true
}
return [string]$actual -eq [string]$Expected
}
$checks = @(
(Test-RegistryValue -Path 'HKCU:\software\policies\microsoft\office\16.0\excel\security' -Name 'blockxllfrominternet' -Expected 1 -Kind DWord)
)
if ($checks -notcontains $false) {
Write-Output 'Compliant'
exit 0
}
Write-Output 'Non-compliant'
exit 1
# === Remediation script ===
# Exported from gporais.com
# Policy: Block Excel XLL Add-ins that come from an untrusted source
# State: Enabled
# Supported on: At least Windows Server 2016, Windows 10
# Warning: In SYSTEM context (the Intune default), HKCU targets the SYSTEM profile. Run this script using the logged-on credentials.
$path = 'HKCU:\software\policies\microsoft\office\16.0\excel\security'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'blockxllfrominternet' -Value 1 -Type DWordBuilding a multi-setting collection? Add this setting and generate combined .reg / PowerShell / GPO scripts.