Squid security advisory 2016:10 reports:
Due to incorrect comparison of request headers Squid can deliver
responses containing private data to clients it should not have
reached.
This problem allows a remote attacker to discover private and
sensitive information about another clients browsing session.
Potentially including credentials which allow access to further
sensitive resources. This problem only affects Squid configured
to use the Collapsed Forwarding feature. It is of particular
importance for HTTPS reverse-proxy sites with Collapsed
Forwarding.
Squid security advisory 2016:11 reports:
Due to incorrect HTTP conditional request handling Squid can
deliver responses containing private data to clients it should not
have reached.
This problem allows a remote attacker to discover private and
sensitive information about another clients browsing session.
Potentially including credentials which allow access to further
sensitive resources..