Thanks for the extra information, indeed disabling the trusted hostname feature seems like the best bet. For now we just changed all websites to point to the canonical name, if we ever have a need to change that we’ll just disable the “trusted hostname”.
Regards,
Mihnea
Piwik was correctly configured (and the code was correct there), however within WP-Piwik we were using an alias of the Piwik server to talk to it — i.e. “machine.example.com” instead of “piwik.example.com”. This used to work correctly until recently, but it is possible more stringent security controls now restrict the behaviour.
Changing the hostname to the “canonical” one (piwik.example.com) used within Piwik fixed the issue. It is still weird that the IPv6 address was showing up there, it may warrant some investigation (a hostname error instead of that behaviour would probably push people in the right direction).
Thanks,
Mihnea
