MC1117115 - Updates to custom scripting in sites and Classic Publishing site creation

We are implementing the following changes to custom scripting and classic publishing in SharePoint Online.

1. Disablement of custom scripting

Custom scripting will be disabled by default (setting DenyAddAndCustomizePages to 1 or $true) for sites created with the following templates:

• BLANKINTERNETCONTAINER#0 = Classic Publishing Portal Site
• CMSPUBLISHING#0 = Classic Publishing Site
• BLANKINTERNET#0 = Classic Publishing Site Blank
• CSPCONTAINER#0 = SharePoint Embedded Site

Refer to this documentation to learn more about the security considerations of ungoverned scripting.

2. Ability to set site property bag valued without requiring custom scripting enablement.

Users no longer need to set DenyAddAndCustomizePages to $false or 0 (i.e. enable custom scripting) in a site to manage site property bag values. We have introduced a new AllowWebPropertyBagUpdateWhenDenyAddAndCustomizePagesIsEnabled setting at the site level and at the tenant level to allow adding/managing site property bag values. Please see documentation here for tenant level setting and here for the site level setting. 

3. Classic publishing sites creation and feature activation changes

Users will no longer be able to create new classic publishing related site collections or activate publishing features in existing site collections. This applies to both UX and API interactions.

Sites collections with the following templates cannot be created:

• BLANKINTERNETCONTAINER#0 = Publishing Portal Site
• CMSPUBLISHING#0 = Publishing Site
• BLANKINTERNET#0 = Publishing Site Blank
• ENTERWIKI#0 = Enterprise Wiki
• SRCHCEN#0 = Enterprise Search Center
• SPSSITES#0 = Site Directory
• SPSNHOME#0 = News Home Site
• PRODUCTCATALOG#0 = Product Catalog
• SPSREPORTCENTER#0 = Report Center
• SPSTOPIC#0 = Topic Area Template

Existing classic publishing enabled site collections are unaffected and can continue regular usage, including creation of sub sites.

When this will happen

Both changes, the extended custom scripting governance and the new classic publishing restrictions, will take effect starting September 15, 2025.

How this will affect your organization

• When custom scripting is disabled in classic publishing sites, users will no longer be able to use script editor web parts, create custom master pages or page layouts, and utilize several other features. More details on features affected when custom scripting is disabled can be viewed in this documentation.

• With the change to stop the creation of new classic publishing site collections and publishing feature activation, SharePoint admins will no longer be able to create new classic publishing enabled site collections or enable publishing features at site collection level.

What you need to do to prepare

We recommend taking the following actions to prepare for these upcoming changes.

1. Inform owners of the classic publishing sites in your organization of these upcoming changes. Promote switching to use of Modern sites. Refer to this guide.

2. To temporarily opt out of the custom scripting enforcement in classic publishing sites for your tenant until March 15, 2026, use the following PowerShell command:

Set-SPOTenant -DelayDenyAddAndCustomizePagesEnforcementOnClassicPublishingSites $true

3. To temporarily opt out of custom scripting enforcement for a specific site (with any template) with tenant admin approval (effective for 24 hours), use the following PowerShell command:

Set-SPOSite <SiteURL> -DenyAddAndCustomizePages $false

4. If you need to allow the creation of new classic publishing site collections or enable publishing feature activations, use the following PowerShell command set the flag to allow.

Set-SPOTenant -AllowClassicPublishingSiteCreation $true

NOTE:

• You need to install the latest (16.0.26211.12010 or higher) SharePoint Online Management Shell in order to run the commands above.
• The DelayDenyAddAndCustomizePagesEnforcementOnClassicPublishingSites command is scheduled to end starting on March 15, 2026, while all other commands are expected to remain functional beyond that date. 

Compliance considerations

There is no impact or change to compliance.

Referenced content

Security considerations of allowing custom script - SharePoint in Microsoft 365 | Microsoft Learn

Allow or prevent custom script - SharePoint in Microsoft 365 | Microsoft Learn

SharePoint modernization guidance | Microsoft Learn