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ASP.NET Browser Definition Files Issues in .NET Framework 4.0


When using Internet Explorer 10, SecureAuth IdP users might encounter the following issues

  • On the Registration / Multi-Factor Methods page, some controls are disabled

  • Complete freeze of Internet Explorer

  • Error message: "Page can't be displayed"

  • Error message using the F12 Developer Tool: "Script Error encountered","'_doPostBack is undefined"

Applies to

SecureAuth IdP Version

OS Version


  • Windows Server 2008

  • Windows Server 2008 R2

  • Windows Server 2012

  • Windows Server 2012 R2


By default, ASP.NET uses sniffing technology for the user agent string to detect browsers. Since the browser definition files only cover a limited range of browser versions, as the version numbers increase, ASP.NET might not recognize new versions of a browser by using the user agent string.

In this scenario, ASP.NET might handle unrecognized versions as an unknown browser. For example, ASP.NET is unable to recognize Windows Internet Explorer 10 which has the following user agent string: Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/6.0)


A hotfix is available for the ASP.NET browser definition files in the Microsoft .NET Framework 4.0. This hotfix introduces updated definitions in the browser definition files for Internet Explorer and for Mozilla Firefox in IIS.