GoodData SSO login using GET links will stop working on March 18. It means that property link in the response of SSO login using GoodData Writer will stop working too.
If you use any custom solution built upon our Writer, you need to migrate it to the new POST login, i.e. take property encryptedClaims from our resource and call this GoodData API call: https://help.gooddata.com/display/doc/API+Reference#/reference/authentication/sso-pgp-login which will login your user. SSO links to GoodData in our Connection UI are already migrated to the new method.