Content Security Policy combined with HTTP to HTTPS redirection can be used by malicious server to verify whether a known site is within a user's browser history. External Reference: https://www.mozilla.org/security/announce/2016/mfsa2016-89.html Acknowledgements: Name: the Mozilla project Upstream: Xiaoyin Liu Statement: This issue does not affect the version of firefox and thunderbird as shipped with Red Hat Enterprise Linux 5, 6 and 7.