SharePoint 2016 Jan 2026 Security Update breaks custom SOAP services – “Type is not registered as safe”

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Hi @Hamid Mahmood Sial

Thank you for posting your question in the Microsoft Q&A forum. 

Based on the information you provided, I understand that after installing the SharePoint Server 2016 Security Update dated January 13, 2026, your custom SOAP (ASMX) services stopped working on Site Pages. When opening pages that contain these services (via DataFormWebPart), the error “The type is not registered as safe” is displayed, although the services were working correctly before applying the security update.

According to the documentation and similar cases, SharePoint currently allows Web Parts and controls that are explicitly declared as safe in the SafeControls configuration. Any custom control or service that is not registered in the SafeControls list of the Web Application may be blocked, which can lead to the error “The type … is not registered as safe” and prevent the page from rendering properly.

This behavior is similar to issues previously observed with workflows, where certain security patches removed or disabled entries under AuthorizedTypes or SafeControls in the web.config file. To restore functionality for your custom SOAP services, you need to register the related custom controls or assemblies in the SafeControls section of the SharePoint configuration. In other words, the Web Part or assembly used by the SOAP service must be explicitly added to the SafeControls list so that SharePoint treats it as “safe.”

However, as a moderator, I do not have the resources to access or troubleshoot specific customer environments directly. Therefore, you may consider raising a support ticket to receive more in-depth assistance from the official support team.

Services Hub

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I hope this information is helpful.

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