On attempting to login into either a front-end account or admin account I'm hit by:
400 Bad Request
Request Header Or Cookie Too Large
It's only happened recently but running the latest Craft CMS v2.5.2757 and from looking at the cookies created during login I think it's possibly related to CSRF protection as deleting the top cookie in the list below fixes the issue until you log in again.
Running a few other Craft sites on the same staging nGinx server without the same issue, and even the same codebase is running another site without issue.
Any thoughts please?!