Anti-forgery token issue (MVC 5)

Try setting (in global.cs):

AntiForgeryConfig.UniqueClaimTypeIdentifier = ClaimTypes.NameIdentifier;

Do you know what claims you do get in your ClaimsIdentity? If not:

1. Remove the [ValidateAntiForgeryToken] attribute
2. Put a breakpoint somewhere in your controller and break at it
3. Then look at the current ClaimsIdentity and examine the claims
4. Find one that you think will uniquely identify your user
5. Set the AntiForgeryConfig.UniqueClaimTypeIdentifier to that claim type
6. Put back the [ValidateAntiForgeryToken] attribute

Just put this in global.asax.cs

AntiForgeryConfig.UniqueClaimTypeIdentifier = ClaimsIdentity.DefaultNameClaimType;