Microsoft Disabling Custom Scripting & Classic Publishing

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Critical Alert: Microsoft Is Disabling Custom Scripting and Classic Publishing Site Creation, Act Before Sept 15, 2025 (MC1117115)

Microsoft has announced a major governance shift via Message Centre Alert MC1117115, targeting custom scripting and classic publishing features in SharePoint Online. These changes will go live starting September 15, 2025, and will impact organisations still relying on legacy functionality for intranet sites, dashboards, or scripted solutions.

What’s Changing?

  1. Custom Scripting Disabled by Default

Custom scripting will be disabled for specific SharePoint site templates by default (DenyAddAndCustomizePages = 1), including:

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

Any use of Script Editor Web Parts, inline JavaScript, or custom master pages/page layouts in these sites will break unless action is taken.

  1. Classic Publishing Site Creation Will Be Blocked

You will no longer be able to create new classic publishing sites or activate the publishing feature on existing sites via the UI or API. Affected templates include:

  • Enterprise Wiki (ENTERWIKI#0)
  • Enterprise Search Centre (SRCHCEN#0)
  • Site Directory, News Home, Product Catalogue, Report Center, Topic Sites, etc.

While existing publishing sites will continue to function, no new publishing site collections will be permitted without explicitly opting in.

  1. New Property Bag Handling

Managing property bag values no longer requires enabling custom scripting.

A new setting AllowWebPropertyBagUpdateWhenDenyAddAndCustomizePagesIsEnabled allows this functionality while maintaining script restrictions.

What This Means for Your Organisation

  •  No more creation of classic publishing sites
  •  Custom scripting (JavaScript, CEWP, SEWP) will be blocked in key site templates
  •  Modernisation delays or governance missteps could break current solutions
  •  Any reliance on page-level scripting, custom branding, or embedded logic is at risk

These changes can and will result in broken functionality if you’re still depending on classic publishing architecture or legacy script-based solutions.

How We Can Help

Our SharePoint experts are ready to:

  • Run a full impact assessment across your tenant
  • Help you migrate away from script-based solutions to SPFx, Power Apps, or Power Automate
  • Modernise classic publishing portals into scalable, secure, and Microsoft-compliant Modern SharePoint sites
  • Provide targeted user training and governance workshops to future-proof your environment

Deadline: September 15, 2025

Optional deferral ends: March 15, 2026

Remediation timelines are short. Don’t wait until critical intranet functions break.

 Contact us now to schedule your Custom Script Risk Assessment and secure your SharePoint investment for the future.

Contact us