Microsoft Is Hardening Entra ID Sign-Ins Against Script Injection
Microsoft will enforce Content Security Policy on Entra ID browser sign-ins through late October 2026. For small businesses, it is a reminder that identity needs more than one layer.
Here Is How Layered Identity Defenses Help
Microsoft is tightening the browser sign-in page for Entra ID, the identity service behind Microsoft 365. Starting mid-October 2026, and finishing by late October, a Content Security Policy will allow only trusted Microsoft CDN scripts to run during authentication. The goal is to block external script injection and cross-site scripting tricks that try to steal credentials on the login page.
What changes for users and admins
According to a Message Center update reported by BleepingComputer, the change is on by default and needs no tenant configuration. People can still sign in even if unsupported script-injection browser tools stop working. Microsoft Authentication Library and API-based flows are unaffected; the policy applies to browser experiences on login.microsoftonline.com. Microsoft asks organizations to stop relying on extensions that inject code into sign-in pages and to test flows in the browser developer console for CSP violations before the deadline.
Why this sits inside a larger push
The update is part of Microsoft’s Secure Future Initiative, launched after Chinese hackers breached Exchange Online mailboxes of many organizations in 2023. In the same vein, Microsoft has disabled ActiveX in Windows Microsoft 365 and Office 2024 apps and updated security defaults to block legacy authentication to Office, SharePoint, and OneDrive.
What this means for your company
A safer sign-in page is one layer, not the whole answer. Treat identity like a stack:
- Keep the platform current. Accept Microsoft’s CSP change, remove brittle login extensions, and test that staff can still authenticate.
- Prefer phishing-resistant factors. Passkeys, security keys, or authenticator apps beat codes that can be relayed (tools such as Microsoft Entra multifactor authentication or Cisco Duo are examples of stronger sign-in options).
- Block legacy protocols. Old mail and file protocols that skip modern sign-in are a common back door; Microsoft’s security defaults already push in that direction.
- Watch the mailbox and the device. Email filtering and endpoint protection catch what identity controls miss (Proofpoint and Bitdefender GravityZone are examples of layers that sit beside Microsoft 365, not instead of it).
Need help layering identity and Microsoft 365 defenses? Reach out to Layer 7 Data Solutions to discuss how we’ve helped companies similar to yours.
Details on the CSP rollout come from BleepingComputer’s report on Microsoft’s Entra ID script-injection protections.
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