This seem to occur randomly, here are the steps that I remember to the best of my abilities:
- Added 6 external users
- Approved all 6 users
- Login witih one of the newly created external users through extranet
- Got error message as below:
value cannot be null.
Parameter name: value at System.string.Endswith(String value, sfrinçComparison comparisonType)
at Microsoft.sharePoint.ApplicabonRuntime.spRequestModule.PostAuthenticateRequestlHlandler(Object oSender, EventArgs ea)
at System.web.HttpApplicabon.SyncEventExecubonStep.System.web.HttpApplication.IExecutionStep.Execute
at System.web.lHlttpApplication.ExecuteStep(IExecutionstep step, Boolean& completedSynchronously)
Troubleshoot issues with Windows SharePoint Services.
And this error persists for any external users that tries to login thereafter until an IISRESET was done.