Trending Issue

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To enhance security September 2025 CU for SharePoint restricts the Windows WSS_WPG windows security group and the IIS_IUSRS windows security group from writing into the SharePoint _LAYOUTS directory (c:\program files\common files\microsoft shared\Web Server Extensions\16\TEMPLATE\LAYOUTS). As the SharePoint Configuration wizard adds the local system account of Windows (NT Authority\system) to the WSS_WPG windows security group, future […]

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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 […]

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After installing SharePoint Workflow Manager August 2025 CU on a machine which does not have a recent patch level of SharePoint Server Subscription Edition installed error messages similar to the following can be found in the logs: Could not load file or assembly ‘System.Memory, Version=4.0.1.1, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51’ or one of its dependencies. Reference: Trending Issue: […]

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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 […]

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Trending Issue: Group claim validation fails in SPSE when editing a Secure Store Target Application after September 2025 CU

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 […]

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Trending Issue: SharePoint SP2010 workflows fail on SPSE after installing September 2025 CU

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. […]

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Trending Issue: SPAdminV4 fails to start on Windows Server 2025 after installing September 2025 CU

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 […]

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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 […]

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Trending Issue: SharePoint fixes fail to install after installation of September 2025 CU

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 […]

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Trending Issue: Classic Workflow Manager Workflows fail after September 2025 CU for SharePoint

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 […]

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Trending Issue: "Copy SideBySide files for In Place Upgrade failed" when running SharePoint Configuration Wizard

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 […]