Information
A Web site's error pages are often set to show detailed error information for troubleshooting purposes during testing or initial deployment. To prevent unauthorized users from viewing this privileged information, detailed error pages must not be seen by remote users. This setting can be modified in the errorMode attribute setting for a Web site's error pages. By default, the errorMode attribute is set in the Web.config file for the Web site or application and is located in the <httpErrors> element of the <system.webServer> section. It is recommended that custom errors be prevented from displaying remotely.
The information contained in custom error messages can provide clues as to how applications function, opening up unnecessary attack vectors. Ensuring custom errors are never displayed remotely can help mitigate the risk of malicious persons obtaining information as to how the application works.
NOTE: This section requires ASP.NET, but ASPNET45 and .Net Extensibility have not been found.