I use the Dropbox PHP SDK. Everything was working fine and suddenly the authentication process no longer works while no changes have been made to the code in this area.
I receive the error 'CSRF Mismatch'.
When looking at all CSRF tokens in the URL all seems to be correct:
https://myapp.herokuapp.com/dropbox/callback.php?state=L9yH1hf7pgiOY7j7fsFegA%3D%3D&code=redacted
CSRF Tokens match. Log reveals they are not though:
[15-May-2015 12:09:44 UTC] /dropbox-auth-finish: CSRF mismatch: Expected 'sW2Zy4OD7YBijNHaeCtyjQ==', got 'L9yH1hf7pgiOY7j7fsFegA=='