Since multiple Trending Issues have now been documented for the September 2025 CU, and it’s becoming increasingly difficult for individuals to keep track, I’ve decided to create a single summary page. Issue Status SharePoint 2013 Workflows fail in combination with Classic Microsoft Workflow Manager after September 2025 CU Warning: Upgrade to SPWFM required before July […]
To enhance security the encryption algorithm used by the secure store service to save credentials has been update to a more secure version. As a side effect credentials stored with the old algorithm can no longer be decrypted. Symptoms When trying to edit an existing target application or when trying to add/update credentials the following […]
To enhance security a new Exploit Protection Setting was added to Windows when installing September 2025 CU. This adds several protections to OWSTIMER.EXE including an option that prevents creating child processes. SharePoint 2010 workflows require the workflow definition to be compiled using the CSC.EXE compiler – and this fails due to this Exploit Protection setting. […]
To enhance security a new Exploit Protection Setting was added to Windows when installing September 2025 CU. This setting works as expected on Windows Server 2022 but causes the SharePoint Administration Service to fail on Windows Server 2025. Symptom When running the SharePoint Configuration Wizard for SharePoint Server Subscription Edition on Windows Server 2025 fails […]
Several customers have reported issues when deploying custom solutions after installing the September 2025 CU for SharePoint Server 2016, 2019, and Subscription Edition. The following error is returned when deploying the solution: Cause The cause of this issue is a combination of new permissions assigned to the WSS_WPG and IIS_IUSRS Windows security groups — intended […]
After installation of September 2025 CU for SharePoint Server 2016, 2019 and Subscription Edition customers might notice a Health Analyzer entry similar to this: Cause September 2025 CU for SharePoint added a deny ACL to the _LAYOUTS directory of SharePoint in the 16 and 14 hive to prevent write access to this folder from accounts […]
Information: The issue described in this article currently affects only customers which executed the SharePoint Configuration Wizard after installing the language independent fix from September 2025 CU and the installation of the language dependent fix. Starting with October 2025 CU for SharePoint Server (all versions) most customers might be affected by this problem – so […]
SharePoint Server 2025 CU for SharePoint Server 2016, 2019 and Subscription Edition includes security hardening for SharePoint Server 2013 workflows which enforces the most recent SharePoint Workflow Manager updates to be installed on SPWFM. As a side effect this also prevents classic workflow manager workflows from running as this version does not comply with this […]
I have received several reports from users that after installing September 2025 CU for SharePoint Server 2016, 2019 or Subscription Edition the SharePoint configuration wizard failed with the following error message: System.InvalidOperationException was thrown. Additional exception information: An internal error occurred. The program cannot continue to run. The program stopped because of the following: Copy […]
To enhance security of SharePoint Server, three new security features are being introduced in September 2025 CU. These enhancements apply to all supported SharePoint versions — 2016, 2019, and Subscription Edition — and I’d like to highlight them in this article: Machine Key Rotation Timer job AMSI enabled for all web applications Test-DefenderAndAmsiWorkProperly Cmdlet to […]
The 25H2 feature update for SharePoint Server Subscription Edition has been released today and is included in the September 2025 CU for SharePoint Server Subscription Edition. About Feature Updates for SharePoint Server Subscription Edition: Releasing new features for a product which is used by a large number of users creates challenges for IT departments, e.g. […]
Below are the security fixes for the SharePoint OnPrem versions released this month. SharePoint Server 2016: KB 5002778 – SharePoint Server 2016 (language independent) KB 5002777 – SharePoint Server 2016 (language dependent) Microsoft Support recommends to install the complete September 2025 CU for SharePoint 2016 rather than individual security fixes. SharePoint Server 2019: KB 5002775 […]
