403 Forbidden: The server understood the request, but is refusing to fulfill it

[larionov_alvl]

Thank you, really helped me!

[n4nagappan]

LOGOUT from your account and try again. That fixed it for me as well. Thanks @Pelham12345

[krotovic]

I was currently facing the same issue trying to apply changes in my settings on twitter.com/settings
but after disabling one browser plugin that changes Origin in request header to enable cross-origin scripts
it works. May this helps someone.