2025-2026 Optimizely CMS 11 release notes
Follow this article to receive email notifications when new Optimizely Content Management System (CMS 11) packages are available for 2024, 2025, and 2026. Product packages are found on the Optimizely NuGet server.
Note
Are you looking for release notes before January 2024? See the Optimizely Release Notes on the Optimizely World site.
You can find prior versions of user guides (2021 and older) and when functionality was released or deprecated at the following locations:
Most recent releases
Date | Release | Type |
|---|---|---|
April 15, 2026 | CMS ConnectForSharepoint 2.4.2 | Bug fix |
April 10, 2026 | Accouncement | |
February 25, 2026 | CMS Core 11.21.5 | Bug fix |
June 30, 2025 | CMS Core 11.21.4 | Enhancements and bug fixes |
April 22, 2025 | CMS Core 11.21.3 | Bug fixes |
February 11, 2025 | CMS UI 11.37.4 | Bug fix |
February 2, 2025 | CMS Azure 11.2.1 | Bug fix |
CMS 11
2025-2026-optimizely-cms-11-release-notes.mdxCMS major version policy—April 10, 2026
- Development All new product development is focused exclusively on the latest major version of CMS. At this time, that is CMS 13. No new functionality will be built for earlier major versions.
- End of Support We provide active support for the current major version and one prior major version. This includes monitoring, triaging, and fixing severe bugs and or any security issues for CMS 12. At this time, CMS 13 and CMS 12 are supported. CMS 11 and earlier are no longer supported.
- End of Life We do not enforce end-of-life by removing access or forcing upgrades. Customers may continue using older major versions. However, major versions older than the supported window will no longer receive support.
EPiServer.CMS.Core
2025-2026-optimizely-cms-11-release-notes.mdx11.21.5—February 25, 2026
Bug fix
- Fixed an issue where you could not upgrade to a higher version due to a package limitation on the transitive Microsoft.Extensions.Options package.
2025-2026-optimizely-cms-11-release-notes.mdx11.21.4—June 30, 2025
Enhancements
A user can embed JavaScript in XhtmlString properties and in uploaded files. Often this is intended, but sometimes it can be malicious. Through configuration, you can specify the following options for MediaUploadMode, XhtmlString, LinkItem and Url when you upload a file with scripts or in other properties.
- Keep = If the file contains JavaScript, then keep and execute it. If a property has JavaScript, allow it.
- Remove = If the file contains JavaScript, remove the script before saving the file. If a property has JavaScript, remove it.
- ThrowException = If the file contains JavaScript, do not upload the file and display an error in the upload dialog box. If a property has JavaScript, display an error.
See Filter JavaScript from properties and filesFilter JavaScript from properties and files.
Bug fixes
- CMS-36261 – Fixed a timing issue that occurred when there were many content types and simultaneous access to certain types. The issue arose because EagerCompileProxies was called in a background thread, and if there are many ContentTypes, it takes time to generate proxies. During this proxy generation, if someone accessed types using AppDomain.CurrentDomain.GetAssemblies() and subsequently attempted to access those types, an exception was thrown.
- CMS-28200 – Fixed an issue where indexing failed due to a license check error during serialization.
2025-2026-optimizely-cms-11-release-notes.mdx11.21.3—April 22, 2025
Bug fixes
- CMS-31794 – Fixed an issue where a vulnerability existed between the SQL client and the SQL server in System.Data.SqlClient NuGet packages. See Microsoft security advisory announcement: https://github.com/dotnet/announcements/issues/292#affected-packages.
- CMS-28027 – Fixed an issue where, when you clicked Stop Job on a custom long-running scheduled job, the job became stuck in a running state and displayed The job is stopping message. There was no change upon reloading the page and you could not start or stop the job from that state. Now, the job stops successfully and a message prompts you to refresh the page to see the updated status.
EPiServer.CMS.UI
2025-2026-optimizely-cms-11-release-notes.mdx11.37.4—February 11, 2025
Bug fix
- CMS-38861 – Fixed a type issue in the tooltip dialog for installations using sv-SE culture.
EPiServer.Azure
2025-2026-optimizely-cms-11-release-notes.mdx11.2.1—January 7, 2025
Bug fix
- CMS-38103 – Fixed an issue by restoring two methods, AzureBlobProvider.Initialize() and AzureBlobProvider.Validate(string connectionString, string containerName) to avoid breaking changes.
EPiServer.ConnectForSharePoint
2025-2026-optimizely-cms-11-release-notes.mdx2.4.2—April 15, 2026
Bug fix
- CMS-51445 – Update the authentication option for SharePoint Online to only allow Modern authentication. Microsoft deprecated cookie-based authentication and Azure ACS app principals. Now, SharePoint Online customers must use Modern (OAuth 2.0) authentication. See Optimizely Connect for SharePoint online.