Block Excel XLL Add-ins that come from an untrusted source

UserNeeds changes for IntuneL_BlockXLLFromInternet

Supported on SUPPORTED_Windows_10_0 (defined in the Windows templates)

5568.1000

What it does

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.

What it writes

Hive: HKEY_CURRENT_USER
Registry key: software\policies\microsoft\office\16.0\excel\security

Why it needs changes for Intune

Policy references a Windows supportedOn definition.
ADMX-INTUNE-WINDOWS-SUPPORTEDON-REFERENCE

Security baselines

Microsoft's Microsoft 365 Apps for Enterprise 2512 sets this to Enabled, in its GPO “MSFT Microsoft 365 Apps v2512 - User”.

blockxllfrominternet: Set to “Block” (1).

Read from the registry.pol files in the baselines' GPO backups, downloaded from Microsoft's Security Compliance Toolkit. All baselines

Options

Option	Type	Registry value	Allowed values
L_BlockXLLFromInternetEnumDefault: Block	Drop-down list	`blockxllfrominternet`	Block`1` Show Additional Warning`0` Allow`2`

Configure and deploy

Choose a state and the option values; the output below is generated from the template for exactly that.

Enabled · User · template defaults

Registry file (.reg)

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\excel\security]
"blockxllfrominternet"=dword:00000001

PowerShell

$ErrorActionPreference = 'Stop'

function Set-RegistryValue {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name,
        [Parameter(Mandatory = $true)][string] $PropertyType,
        [Parameter(Mandatory = $true)][object] $Value
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        New-Item -Path $Path -Force | Out-Null
    }

    New-ItemProperty -LiteralPath $Path -Name $Name -PropertyType $PropertyType -Value $Value -Force | Out-Null
}

function Remove-RegistryValue {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name
    )

    if (Test-Path -LiteralPath $Path) {
        Remove-ItemProperty -LiteralPath $Path -Name $Name -Force -ErrorAction SilentlyContinue
    }
}

function Clear-RegistryKeyValues {
    param(
        [Parameter(Mandatory = $true)][string] $Path
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        return
    }

    foreach ($propertyName in (Get-Item -LiteralPath $Path).Property) {
        Remove-ItemProperty -LiteralPath $Path -Name $propertyName -Force -ErrorAction SilentlyContinue
    }
}

# Policy: Block Excel XLL Add-ins that come from an untrusted source
# Name: L_BlockXLLFromInternet
# Scope: User
# State: Enabled
# Source: excel16.admx

Set-RegistryValue -Path 'Registry::HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\excel\security' -Name 'blockxllfrominternet' -PropertyType 'DWord' -Value 1

The OMA-URI is an inferred ADMX-backed Policy CSP candidate derived from the source ADMX file name and policy name.
Some Microsoft policies use built-in Policy CSP pages whose area names don't match the ADMX file name, so verify the candidate against Microsoft Learn before deployment.

ADMX profile candidate (OMA-URI)

./User/Vendor/MSFT/Policy/Config/ADMX_excel16/L_BlockXLLFromInternet

ADMX SyncML candidate

<SyncML xmlns="SYNCML:SYNCML1.2">
  <SyncBody>
    <Replace>
      <CmdID>1</CmdID>
      <Item>
        <Meta>
          <Format>chr</Format>
          <Type>text/plain</Type>
        </Meta>
        <Target>
          <LocURI>./User/Vendor/MSFT/Policy/Config/ADMX_excel16/L_BlockXLLFromInternet</LocURI>
        </Target>
        <Data>&lt;enabled/&gt;
&lt;data id="L_BlockXLLFromInternetEnum" value="0"/&gt;</Data>
      </Item>
    </Replace>
    <Final/>
  </SyncBody>
</SyncML>

Intune remediation scripts

Detection

$ErrorActionPreference = 'Stop'
$reasons = [System.Collections.Generic.List[string]]::new()

function Test-RegistryValueExists {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        return $false
    }

    return $null -ne (Get-ItemProperty -LiteralPath $Path -Name $Name -ErrorAction SilentlyContinue)
}

function Test-RegistryValueEquals {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name,
        [Parameter(Mandatory = $true)][string] $Kind,
        [Parameter(Mandatory = $true)][object] $Expected
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        return $false
    }

    $valueObject = Get-ItemProperty -LiteralPath $Path -Name $Name -ErrorAction SilentlyContinue
    if ($null -eq $valueObject) {
        return $false
    }

    $actual = $valueObject.$Name
    switch ($Kind) {
        'String' { return [string]$actual -ceq [string]$Expected }
        'ExpandString' { return [string]$actual -ceq [string]$Expected }
        'DWord' { return [uint32]$actual -eq [uint32]$Expected }
        'QWord' { return [uint64]$actual -eq [uint64]$Expected }
        'MultiString' {
            $actualArray = @($actual)
            $expectedArray = @($Expected)
            if ($actualArray.Count -ne $expectedArray.Count) { return $false }
            for ($index = 0; $index -lt $actualArray.Count; $index++) {
                if ([string]$actualArray[$index] -cne [string]$expectedArray[$index]) { return $false }
            }
            return $true
        }
        'Binary' {
            $actualArray = [byte[]]$actual
            $expectedArray = [byte[]]$Expected
            if ($actualArray.Length -ne $expectedArray.Length) { return $false }
            for ($index = 0; $index -lt $actualArray.Length; $index++) {
                if ($actualArray[$index] -ne $expectedArray[$index]) { return $false }
            }
            return $true
        }
        default { return [string]$actual -ceq [string]$Expected }
    }
}

# Policy: Block Excel XLL Add-ins that come from an untrusted source
# Name: L_BlockXLLFromInternet
# Scope: User
# State: Enabled
# Source: excel16.admx

$isMatch = Test-RegistryValueEquals -Path 'Registry::HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\excel\security' -Name 'blockxllfrominternet' -Kind 'DWord' -Expected 1
if (-not $isMatch) {
    $reasons.Add('Value mismatch: HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\excel\security\blockxllfrominternet') | Out-Null
}

if ($reasons.Count -eq 0) {
    Write-Output 'Compliant'
    exit 0
}

$reasons | ForEach-Object { Write-Output $_ }
exit 1

Remediation

$ErrorActionPreference = 'Stop'

function Set-RegistryValue {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name,
        [Parameter(Mandatory = $true)][string] $PropertyType,
        [Parameter(Mandatory = $true)][object] $Value
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        New-Item -Path $Path -Force | Out-Null
    }

    New-ItemProperty -LiteralPath $Path -Name $Name -PropertyType $PropertyType -Value $Value -Force | Out-Null
}

function Remove-RegistryValue {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name
    )

    if (Test-Path -LiteralPath $Path) {
        Remove-ItemProperty -LiteralPath $Path -Name $Name -Force -ErrorAction SilentlyContinue
    }
}

function Clear-RegistryKeyValues {
    param(
        [Parameter(Mandatory = $true)][string] $Path
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        return
    }

    foreach ($propertyName in (Get-Item -LiteralPath $Path).Property) {
        Remove-ItemProperty -LiteralPath $Path -Name $propertyName -Force -ErrorAction SilentlyContinue
    }
}

# Policy: Block Excel XLL Add-ins that come from an untrusted source
# Name: L_BlockXLLFromInternet
# Scope: User
# State: Enabled
# Source: excel16.admx

Set-RegistryValue -Path 'Registry::HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\excel\security' -Name 'blockxllfrominternet' -PropertyType 'DWord' -Value 1

History 1 retained release

5568.100010 Aug 2026
- Already present in the first release ChangeIntel keeps.

Template

Internal name: L_BlockXLLFromInternet
Namespace: excel16.Office.Microsoft.Policies.Windows
Template file: excel16.admx
Release: Microsoft 365 Apps 5568.1000 · file set 8be05d876aae137d…

Definition, editor controls and support

Definition

<policy class="User" displayName="$(string.L_BlockXLLFromInternet)" explainText="$(string.L_BlockXLLFromInternetExplain)" key="software\policies\microsoft\office\16.0\excel\security" name="L_BlockXLLFromInternet" presentation="$(presentation.L_SetDefaultBlockXllFromInternetBehavior)" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="excel16.Office.Microsoft.Policies.Windows:L_TrustCenter" />
      <supportedOn ref="Microsoft.Policies.Windows:SUPPORTED_Windows_10_0" />
      <elements>
        <enum id="L_BlockXLLFromInternetEnum" valueName="blockxllfrominternet">
          <item displayName="$(string.L_BlockXLLInternet)">
            <value>
              <decimal value="1" />
            </value>
          </item>
          <item displayName="$(string.L_PromptXLLInternet)">
            <value>
              <decimal value="0" />
            </value>
          </item>
          <item displayName="$(string.L_AllowXLLInternet)">
            <value>
              <decimal value="2" />
            </value>
          </item>
        </enum>
      </elements>
    </policy>

Editor controls

<presentation id="L_SetDefaultBlockXllFromInternetBehavior" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
        <dropdownList defaultItem="0" noSort="true" refId="L_BlockXLLFromInternetEnum">
        </dropdownList>
      </presentation>

Supported platforms and category

excel16.Office.Microsoft.Policies.Windows:category:L_ExcelOptions
<category displayName="$(string.L_ExcelOptions)" name="L_ExcelOptions" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="excel16.Office.Microsoft.Policies.Windows:L_MicrosoftOfficeExcel" />
    </category>
excel16.Office.Microsoft.Policies.Windows:category:L_MicrosoftOfficeExcel
<category displayName="$(string.L_MicrosoftOfficeExcel)" name="L_MicrosoftOfficeExcel" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions" />
excel16.Office.Microsoft.Policies.Windows:category:L_Security
<category displayName="$(string.L_Security)" name="L_Security" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="excel16.Office.Microsoft.Policies.Windows:L_ExcelOptions" />
    </category>
excel16.Office.Microsoft.Policies.Windows:category:L_TrustCenter
<category displayName="$(string.L_TrustCenter)" name="L_TrustCenter" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="excel16.Office.Microsoft.Policies.Windows:L_Security" />
    </category>
excel16.Office.Microsoft.Policies.Windows:unresolved:Microsoft.Policies.Windows:SUPPORTED_Windows_10_0
<unresolved reference="Microsoft.Policies.Windows:SUPPORTED_Windows_10_0" />
excel16.Office.Microsoft.Policies.Windows:category:L_ExcelOptions
<category displayName="$(string.L_ExcelOptions)" name="L_ExcelOptions" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="excel16.Office.Microsoft.Policies.Windows:L_MicrosoftOfficeExcel" />
    </category>
<strings><string id="excel16.Office.Microsoft.Policies.Windows:L_ExcelOptions">Excel Options</string></strings>
excel16.Office.Microsoft.Policies.Windows:category:L_MicrosoftOfficeExcel
<category displayName="$(string.L_MicrosoftOfficeExcel)" name="L_MicrosoftOfficeExcel" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions" />
<strings><string id="excel16.Office.Microsoft.Policies.Windows:L_MicrosoftOfficeExcel">Microsoft Excel 2016</string></strings>
excel16.Office.Microsoft.Policies.Windows:category:L_Security
<category displayName="$(string.L_Security)" name="L_Security" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="excel16.Office.Microsoft.Policies.Windows:L_ExcelOptions" />
    </category>
<strings><string id="excel16.Office.Microsoft.Policies.Windows:L_Security">Security</string></strings>
excel16.Office.Microsoft.Policies.Windows:category:L_TrustCenter
<category displayName="$(string.L_TrustCenter)" name="L_TrustCenter" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="excel16.Office.Microsoft.Policies.Windows:L_Security" />
    </category>
<strings><string id="excel16.Office.Microsoft.Policies.Windows:L_TrustCenter">Trust Center</string></strings>