Symptoms
An ASPX file cannot be displayed when you try to create it as a custom web part. When this issue occurs, the following error entry and "92liq" event tag are logged in SharePoint Unified Logging System (ULS) logs:
Blocking control with property traversal markup. [tagName: <TagName>][propName: <UnsafePropertyName>][type: <PropertyType>]
Cause
This issue occurs because an unsafe property name is set for a tag in this ASPX file.
Status
This new behavior is by design to strengthen security in SharePoint Server.
Workaround
Note: Users can bypass this security improvement if it's necessary for your web part. Make sure that your web part can use these property names safely before you follow these steps to re-enable the web parts in SharePoint Server.
If you are the farm administrator, you can work around this issue by adding the property name to the WebPartSupportedSimplePropertyNames or WebPartSupportedBoundPropertyNames list in the SharePoint Management Shell:
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If <PropertyType> is SimplePropertyEntry, run the following commands:add-pssnapin *$f=get-spfarm$f.AddGenericAllowedListValue("WebPartSupportedSimplePropertyNames","<UnsafePropertyName>")$f.update()iisreset
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If <PropertyType> is BoundPropertyEntry, run the following commands:add-pssnapin *$f=get-spfarm$f.AddGenericAllowedListValue("WebPartSupportedBoundPropertyNames","<UnsafePropertyName>")$f.update()iisreset
