One of the session cookies that stores state for pending sign-in requests contains incorrectly formatted data. Cookie: %1 ...

One of the session cookies that stores state for pending sign-in requests contains incorrectly formatted data. 
Cookie: %1 
Formatting error: %2 

This cookie is written by AD FS for AD FS use. This error indicates that the cookie has been tampered with. The authentication has failed, and the client request will be denied.